Continuous-wave radar system for detecting ferrous and non-ferrous metals in saltwater environments

ABSTRACT

The present invention includes systems and methods for a continuous-wave (CW) radar system for detecting, geolocating, identifying, discriminating between, and mapping ferrous and non-ferrous metals in brackish and saltwater environments. The radar system (e.g., the CW radar system) generates multiple extremely low frequency (ELF) electromagnetic waves simultaneously and uses said waves to detect, locate, and classify objects of interest. These objects include all types of ferrous and non-ferrous metals, as well as changing material boundary layers (e.g., soil to water, sand to mud, rock to organic materials, water to air, etc.). The radar system (e.g., the CW radar system) is operable to detect objects of interest in near real time.

CROSS REFERENCES TO RELATED APPLICATIONS

This application is a continuation-in-part of U.S. Pat. Application No.17/830,035, filed Jun. 1, 2022, which is a continuation of U.S. Pat.Application No. 17/498,420, filed Oct. 11, 2021, which is a continuationof U.S. Pat. Application 17/033,046, filed Sep. 25, 2020, which claimspriority from U.S. Provisional Pat. Application 62/978,021, filed Feb.18, 2020, each of which is incorporated herein by reference in itsentirety.

BACKGROUND OF THE INVENTION 1. Field of the Invention

The present invention relates to continuous-wave radar systems and morespecifically to detecting ferrous and non-ferrous metals in saltwaterenvironments.

2. Description of the Prior Art

It is generally known in the prior art to provide devices capable ofpropagating electromagnetic waves through bodies of water, includingseawater and brackish water.

Prior art patent documents include the following:

U.S. Pat. Pub. No. 2016/0266246 for A system for monitoring a maritimeenvironment by inventor Hjelmstad, filed Oct. 23, 2014 and publishedSep. 15, 2016, is directed to a system for monitoring a maritimeenvironment, the system including a plurality of detection devices fordetecting objects in the maritime environment, the detection devicesbeing configured for object detection according to different objectdetection schemes, and a data processing device having a communicationinterface and a processor, wherein the communication interface isconfigured to receive detection signals from the detection devices, andwherein the processor is configured to determine locations of theobjects in the maritime environment upon the basis of the receiveddetection signals within a common coordinate system.

U.S. Pat. Pub. No. 2013/0278439 for Communication between a sensor and aprocessing unit of a metal detector by inventors Stamatescu, et al.,filed Jun. 20, 2013 and published Oct. 24, 2013, is directed to a methodfor improving a performance of a metal detector, including: generating atransmit signal; generating a transmit magnetic field based on thetransmit signal for transmission using a magnetic field transmitter;sending a receive signal based on a receive magnetic field received by amagnetic field receiver to a processing unit of the metal detector;sending a communication signal, including information from a sensor, tothe processing unit; and processing the receive signal with thecommunication signal to produce an indicator output signal indicating apresence of a target under an influence of the transmit magnetic field;wherein one or more characteristics of the communication signal areselected based on the transmit signal to reduce or avoid an interferenceof the communication signal to the receive signal.

U.S. Pat. No. 8,604,986 for Device for propagation of electromagneticwaves through water by inventor Lucas, filed May 14, 2009 and issuedDec. 10, 2013, is directed to an invention concerning a device forpropagating electromagnetic waves through impure water such as seawateror brackish water. The device comprises a body of polar material, forexample pure water, contained in an enclosure, and an antenna arrangedto emit an electromagnetic signal into the polar material. Excitation ofdipoles in the polar material by the electromagnetic signal causes themto re-radiate the signal, which is thereby emitted into and relativelyefficientlypropagated through the water in which the device issubmerged. The device offers the possibility of improved underwatercommunication.

U.S. Pat. Pub. No. 2018/0267140 for High spatial resolution 3D radarbased on a single sensor by inventors Corcos, et al., filed Mar. 20,2017 and published Sep. 20, 2018, is directed to a novel system thatallows for 3D radar detection that simultaneously captures the lateraland depth features of a target is disclosed. This system uses only asingle transceiver, a set of delay-lines, and a passive antenna array,all without requiring mechanical rotation. By using the delay lines, aset of beat frequencies corresponding to the target presence can begenerated in continuous wave radar systems. Likewise, in pulsed radarsystems, the delays also allow the system to determine the 3D aspects ofthe target(s). Compared to existing solutions, the system allows for theimplementation of simple, reliable, and power efficient 3D radars.

U.S. Pat. Pub. No. 2002/0093338 for Method and apparatus fordistinguishing metal objects employing multiple frequency interrogationby inventor Rowan, filed Feb. 11, 2002 and published Jul. 18, 2002, isdirected to a method and apparatus for distinguishing metal objectsemploying multiple frequency interrogation. In one aspect, the methodincludes interrogating a target with at least two frequencies, obtainingrespective response signals for the two frequencies, resolving theresponse signals into at least respective resistive component portions,comparing the magnitudes of at least two of the resistive componentportions, selecting one response signal from among the response signalsbased on the comparison, and characterizing the target with the selectedresponse signal. In other aspects, the method includes obtainingresponse data by interrogating the target at at least two frequencies,normalizing theresponse data and comparing the normalized response data.A signal is provided indicating the extent of any disagreement in thenormalized response data.

U.S. Pat. Pub. No. 2014/0012505 for Multiple-component electromagneticprospecting apparatus and method of use thereof by inventor Smith, filedMar. 27, 2012 and published Jan. 9, 2014, is directed to systems andmethods for the detection of conductive bodies using three-componentelectric or magnetic dipole transmitters. The fields from multipletransmitters can be combined to enhance fields at specific locations andin specific orientation. A one- two- or three-component receiver orreceiver array is provided for detecting the secondary field radiated bya conductive body. The data from multiple receivers can be combined toenhance the response at a specific sensing location with a specificorientation. Another method is provided in which a three-componenttransmitter and receiver are separated by an arbitrary distance, andwhere the position and orientation of the receiver relative to thetransmitter are calculated, allowing the response of a highly conductivebody to be detected.

U.S. Pat. No. 10,101,438 for Noise mitigation in radar systems byinventors Subburaj, et al., filed Apr. 15, 2015 and issued Oct. 16,2018, is directed to a noise-mitigated continuous-wavefrequency-modulated radar including, for example, a transmitter forgenerating a radar signal, a receiver for receiving a reflected radarsignal and comprising a mixer for generating a baseband signal inresponse to the received radar signal and in response to a localoscillator (LO) signal, and a signal shifter coupled to at least one ofthe transmitter, LO input of the mixer in the receiver and the basebandsignal generated by the mixer. The impact of amplitude noise or phasenoise associated with interferers, namely, for example, strongreflections from nearby objects, and electromagnetic coupling fromtransmit antenna to receive antenna, on the detection of othersurrounding objects is reduced by configuring the signal shifter inresponse to an interferer frequency and phase offset.

U.S. Pat. No. 7,755,360 for Portable locator system with jammingreduction by inventor Martin, filed Apr. 21, 2008 and issued Jul. 13,2010, is directed to a portable self-standing electromagnetic (EM) fieldsensing locator system with attachments for finding and mapping buriedobjects such as utilities and with intuitive graphical user interface(GUI) displays. Accessories include a ground penetrating radar (GPR)system with a rotating Tx/Rx antenna assembly, a leak detection system,a multi-probe voltage mapping system, a man-portable laser-range findersystem with embedded dipole beacon and other detachable accessory sensorsystems are accepted for attachment to the locator system forsimultaneous operation in cooperation with the basic locator system. Theintegration of the locator system with one or more additional devices,such as fault-finding, geophones and conductance sensors, facilitatesthe rapid detection and localization of many different types of buriedobjects.

U.S. Pat. No. 8,237,560 for Real-time rectangular-wave transmittingmetal detector platform with user selectable transmission and receptionproperties by inventor Candy, filed Oct. 11, 2011 and issued Aug. 7,2012, is directed to a highly flexible real-time metal detector platformwhich has a detection capability for different targets and applications,where the operator is able to alter synchronous demodulationmultiplication functions to select different types or mixtures ofdifferent types to be applied to different synchronous demodulators, andalso different waveforms of the said synchronous demodulationmultiplication functions; examples of the different types beingtime-domain, square-wave, sine-wave or receive signal weightedsynchronous demodulation multiplication functions. The operator canalter the fundamental frequency of the repeating switchedrectangular-wave voltage sequence, and anoperator may alter the waveformof the repeating switched rectangular-wave voltage sequence andcorresponding synchronous demodulation multiplication functions.

U.S. Pat. Pub. No. 2005/0212520 for Subsurface electromagneticmeasurements using cross-magnetic dipoles by inventors Homan, et al.,filed Mar. 29, 2004 and published Sep. 29, 2005, is directed to sensorassemblies including transmitter and receiver antennas to respectivelytransmit or receive electromagnetic energy. The sensor assemblies aredisposed in downhole tools adapted for subsurface disposal. The receiveris disposed at a distance less than six inches (15 cm) from thetransmitter on the sensor body. The sensor transmitter or receiverincludes an antenna with its axis tilted with respect to the axis of thedownhole tool. A sensor includes a tri-axial system of antennas. Anothersensor includes a cross-dipole antenna system.

U.S. Pat. Pub. No. 2017/0307670 for Systems and methods for locatingand/or mapping buried utilities using vehicle-mounted locating devicesby inventor Olsson, filed Apr. 25, 2017 and published Oct. 26, 2017, isdirected to systems and methods for locating and/or mapping buriedutilities. The publication discloses one or more magnetic field sensinglocating devices include antenna node(s) to sense magnetic field signalsemitted from a buried utility and a processing unit to receive thesensed magnetic field signals may be mounted on a vehicle. The receivedmagnetic field signals may be processed in conjunction with sensedvehicle velocity data to determine information associated with locationof the buried utility such as depth and position.

U.S. Pat. Pub. No. 2011/0136444 for Transmit and receive antenna byinventor Rhodes, et al., filed Dec. 9, 2009 and published Jun. 9, 2011,is directed to a transmit/receive antenna for transmission and receptionof electromagnetic signals. The transmit/receive antenna comprises a TXsection and an RX section, where the TX sectioncomprises a magneticallycoupled TX element and a TX input terminal and the RX section comprisesat least one magnetically coupled RX element and has an RX outputterminal. Axes of the TX loop element and the at least one magneticallycoupled RX solenoid element are parallel. Moreover, the at least onemagnetically coupled RX element is positioned to provide high isolationat the RX terminal of the antenna from TX electrical signals fed to theTX input. Specifically, the at least one magnetically coupled RX elementis positioned at a so that the net magnetic flux generated by the TXloop element and threading the RX solenoid element is zero.

U.S. Pat. Pub. No. 2008/0224704 for Apparatus and method for detectingand identifying ferrous and non-ferrous metals by inventor Westersten,filed Sep. 9, 2005 and published Sep. 18, 2008, is directed to a metaldetector using a linear current ramp followed by an abrupt currenttransition to energize the transmitter coil. The constant emf imposed onthe target during the current ramp permits separation of transientvoltages generated in response to eddy currents in the target and itsenvironment from the voltages arising as a result of an inductiveimbalance of the coil system. The temporal separation of the variousvoltages makes reliable differentiation between ferrous and non-ferroustargets possible.

SUMMARY OF THE INVENTION

The present invention relates to a radar system, and particularly acontinuous-wave (CW) radar system for detecting ferrous and non-ferrousmetals in underwater (e.g., saltwater) environments.

It is an object of this invention to provide a radar system (e.g., CWradar system) for detecting ferrous and non-ferrous metals in underwater(e.g., saltwater) environments, increasing radar geolocation accuracy,enabling the identification of the type of material of a target object,discriminating between ferrous and non-ferrous target objects,determining the size and shape of a target object, and mapping targetobjects onto a 2D and 3D coordinate system (e.g., absolute and/orrelative).

In one embodiment, the present invention provides a radar system fordetecting ferrous and non-ferrous metals in an underwater environment,including at least one support vessel, an antenna system including atleast one signal generator, at least one transmitter (Tx) antenna, atleast one receiver (Rx) antenna, and at least one signal processor,wherein the at least one Tx antenna and the at least one Rx antenna arefixed in a cross-polarized orientation with each other or electricallyisolated by distance and/or topography, wherein the at least one Rxantenna is substantially perpendicular to a direction of travel of theat least one support vessel, wherein the at least one signal generatoris operable to emit at least one transmission signal to a target areathrough the at least one Tx antenna, wherein the at least one Rx antennais operable to receive at least one return signal from the target area,wherein the at least one signal processor is operable to analyze the atleast one return signal, wherein the at least one signal processor isoperable to detect and/or locate at least one target object in thetarget area based on the at least one return signal, and wherein theunderwater environment is a saltwater environment.

In another embodiment, the present invention provides a radar system fordetecting ferrous and non-ferrous metals in an underwater environment,including at least one support vessel, an antenna system including atleast one signal generator, at least one transmitter (Tx) antenna, atleast one receiver (Rx) antenna, and at least one signal processor,wherein the at least one Tx antenna and the at least one Rx antenna arefixed in a cross-polarized orientation with each other or electricallyisolated by distance and/or topography, wherein the at least one Rxantenna is substantially perpendicular to a direction of travel of theat least one support vessel, and a geolocation system, wherein the atleast one signal generator is operable to emit at least one transmissionsignal to a target area through the at least one Tx antenna, wherein theat least one Rx antenna is operable to receive at least one returnsignal from the target area, wherein the at least one signal processoris operable to analyze the at least one return signal, wherein the atleast one signal processor is operable to detect and/or locate at leastone target object in the target area based on the at least one returnsignal, wherein the at least one signal processor is operable todetermine a relative geolocation and/or an absolute geolocation of theat least one target object using the geolocation system, and wherein theunderwater environment is a saltwater environment.

In yet another embodiment, the present invention provides a method fordetecting ferrous and non-ferrous metals in an underwater environment,including at least one support vessel traversing a target area, at leastone signal generator emitting at least one transmission signal to thetarget area through at least one transmitter (Tx) antenna, at least onereceiver (Rx) antenna receiving at least one return signal from thetarget area, at least one signal processor analyzing the at least onereturn signal, and the at least one signal processor detecting and/orlocating at least one target object in the target area based on the atleast one return signal, wherein the at least one Tx antenna and the atleast one Rx antenna are fixed in a cross-polarized orientation witheach other, wherein the at least one Rx antenna is substantiallyperpendicular to a direction of travel of the at least one supportvessel, and wherein the underwater environment is a saltwaterenvironment.

These and other aspects of the present invention will become apparent tothose skilled in the art after a reading of the following description ofthe preferred embodiment when considered with the drawings, as theysupport the claimed invention.

BRIEF DESCRIPTION OF THE DRAWINGS

The patent or application file contains at least one drawing executed incolor. Copies of this patent or patent application publication withcolor drawing(s) will be provided by the Office upon request and paymentof the necessary fee.

FIG. 1A illustrates a block diagram of a continuous-wave (CW) radarsystem according to one embodiment of the present invention.

FIG. 1B illustrates a pipe frame for a radar system (e.g., a CW radarsystem) according to another embodiment of the present invention.

FIG. 1C illustrates a radar system (e.g., a CW radar system) accordingto yet another embodiment of the present invention.

FIG. 1D illustrates the radar system (e.g., the CW radar system) of FIG.1C showing the location of antennas in the piping according to anotherembodiment of the present invention operable to transmit and receive atleast two frequencies simultaneously.

FIG. 1E illustrates a side view of a radar system (e.g., a CW radarsystem) according to one embodiment of the present invention operable totransmit and receive at least three frequencies simultaneously.

FIG. 1F illustrates a top view of a radar system (e.g., a CW radarsystem) according to one embodiment of the present invention operable totransmit and receive at least three frequencies simultaneously.

FIG. 1G illustrates a front view of a radar system (e.g., a CW radarsystem) according to one embodiment of the present invention operable totransmit and receive at least three frequencies simultaneously.

FIG. 1H illustrates a port view of a radar system (e.g., a CW radarsystem) according to one embodiment of the present invention operable totransmit and receive at least three frequencies simultaneously usingmodular antenna assemblies.

FIG. 1I illustrates a starboard view of a radar system (e.g., a CW radarsystem) according to one embodiment of the present invention operable totransmit and receive at least three frequencies simultaneously usingmodular antenna assemblies.

FIG. 1J illustrates a radar corner reflector used during calibration ofthe radar system (e.g., the CW radar system) according to one embodimentof the present invention.

FIG. 2 illustrates an antenna setup for Transmitter (Tx) and Receiver(Rx) antennas for a radar system (e.g., a CW radar system) according toone embodiment of the present invention.

FIG. 3A illustrates a cross-polarization orientation for Tx and Rxantennas according to one embodiment of the present invention.

FIG. 3B illustrates a cross-polarization orientation for Tx and Rxantennas according to another embodiment of the present invention.

FIG. 3C illustrates a cross polarization orientation for Tx and Rxantennas according to another embodiment of the present invention.

FIG. 4 illustrates an antenna setup for Tx and Rx antennas for a radarsystem (e.g., a CW radar system) according to one embodiment of thepresent invention.

FIG. 5 illustrates an antenna setup for Tx and Rx antennas with anindication of return length differences between Rx antennas for a radarsystem (e.g., a CW radar system) according to one embodiment of thepresent invention.

FIG. 6 illustrates a phase shift between Rx antennas for a radar system(e.g., a CW radar system) according to one embodiment of the presentinvention.

FIG. 7A illustrates variances in signal strength between Rx₁ and Rx₂antennas for the Rx₁ antenna according to one embodiment of the presentinvention.

FIG. 7B illustrates variances in signal strength between Rx₁ and Rx₂antennas for the Rx₂ antenna according to one embodiment of the presentinvention.

FIG. 7C illustrates variances in frequency using a lower frequencyaccording to on embodiment of the present invention.

FIG. 7D illustrates variances in frequency using a Tx frequencyaccording to one embodiment of the present invention.

FIG. 7E illustrates variances in frequency when using a higher frequencyaccording to one embodiment of the present invention.

FIG. 8 illustrates object detection ranges for a radar system (e.g., aCW radar system) that result from constructive and destructive zonesaccording to one embodiment of the present invention.

FIG. 9 illustrates a precision detector for a radar system (e.g., a CWradar system) according to one embodiment of the present invention.

FIG. 10 illustrates a graph indicating constructive and destructivezones associated with locating an object in a saltwater environmentaccording to one embodiment of the present invention.

FIG. 11A illustrates a graph indicating the energy product for a radarsystem (e.g., a CW radar system) according to one embodiment of thepresent invention.

FIG. 11B illustrates a graph indicating antenna signal strengthassociated with constructive and destructive zones of a radar system(e.g., a CW radar system) according to one embodiment of the presentinvention.

FIG. 11C illustrates a graph indicating a fore and aft antenna energyproduct associated with constructive and destructive zones of a radarsystem (e.g., a CW radar system) according to one embodiment of thepresent invention.

FIG. 12A illustrates a three-dimensional (3D) underwater depth mapindicating numerous objects detected by a radar system at multipledepths below the ocean floor (e.g., a CW radar system) according to oneembodiment of the present invention.

FIG. 12B illustrates a 3D underwater depth map indicating multipleobjects detected by a radar system (e.g., a CW radar system) accordingto one embodiment of the present invention.

FIG. 13A illustrates a 3D underwater heat map indicating the location ofobjects according to one embodiment of the present invention.

FIG. 13B lists all the labels in FIG. 13A representing differentgeographic locations for detected objects according to one embodiment ofthe present invention.

FIG. 14 illustrates a two-dimensional (2D) underwater heat mapindicating location coordinates for a detected object according to oneembodiment of the present invention.

FIG. 15A illustrates a 2D underwater depth map indication locationcoordinates for detected objects according to another embodiment of thepresent invention.

FIG. 15B lists all the labels in FIG. 15A representing differentgeographic locations for detected objects according to one embodiment ofthe present invention.

FIG. 16A illustrates a surveying operation with a radar system (e.g., aCW radar system) according to one embodiment of the present invention.

FIG. 16B illustrates a surveying operation with a radar system (e.g., aCW radar system) connected to a towing vessel according to oneembodiment of the present invention.

FIG. 17A illustrates a 2D underwater heatmap indicating the geolocationof detected objects according to one embodiment of the presentinvention.

FIG. 17B lists all the labels in FIG. 17A representing differentpriority zones on a 2D underwater heatmap for a radar system (e.g., a CWradar system) according to one embodiment of the present invention.

FIG. 18 illustrates a 2D underwater heatmap indicating the geolocationof detected objects according to another embodiment of the presentinvention.

FIG. 19A illustrates a 2D underwater heatmap indicating the geolocationof detected objects according to another embodiment of the presentinvention.

FIG. 19B lists all the labels in FIG. 19A representing differentpriority zones on a 2D underwater heatmap for a radar system (e.g., a CWradar system) according to one embodiment of the present invention.

FIG. 20A illustrates a 2D underwater heatmap indicating a radar system(e.g., a CW radar system) traveling path and the geolocation of detectedobjects according to another embodiment of the present invention.

FIG. 20B lists all the labels in FIG. 20A representing differentgeographic locations for detected objects according to one embodiment ofthe present invention.

FIG. 21A illustrates a 2D graph indicating a land mass and a travelroute for a radar system (e.g., a CW radar system) according to oneembodiment of the present invention.

FIG. 21B illustrates a 2D heatmap graph indicating a travel route for aradar system (e.g., a CW radar system) according to one embodiment ofthe present invention.

FIG. 22A illustrates a circuit diagram of an amplifier board for a radarsystem (e.g., a CW radar system) according to one embodiment of thepresent invention.

FIG. 22B illustrates a pin configuration diagram for an amplifier boardfor a radar system (e.g., a CW radar system) according to one embodimentof the present invention.

FIG. 22C illustrates a pin connection diagram for an amplifier board fora radar system (e.g., a CW radar system) according to one embodiment ofthe present invention.

FIG. 22D illustrates a pin configuration and function diagram for anamplifier board for a radar system (e.g., a CW radar system) accordingto another embodiment of the present invention.

FIG. 22E illustrates a pin configuration and function diagram for anamplifier board for a radar system (e.g., a CW radar system) accordingto another embodiment of the present invention.

FIG. 22F illustrates a chart depicting the flow of signal through anamplifier board for a radar system (e.g., a CW radar system) accordingto one embodiment of the present invention.

FIG. 23 is a table for a primary gain stage of an amplifier board for aradar system (e.g., a CW radar system) according to one embodiment ofthe present invention.

FIG. 24 is a table for a secondary gain stage of an amplifier board fora radar system (e.g., a CW radar system) according to one embodiment ofthe present invention.

FIG. 25 is a table for Stage One and Stage Two gain settings for anamplifier board for a radar system (e.g., a CW radar system) accordingto one embodiment of the present invention.

FIG. 26 is a table for gain calculations for an amplifier board for aradar system (e.g., a CW radar system) according to one embodiment ofthe present invention.

FIG. 27 is a table for Stage One and Stage Two gain settings for anamplifier board for a radar system (e.g., a CW radar system) accordingto another embodiment of the present invention.

FIG. 28A is a table for resistance values for an amplifier board for aradar system (e.g., a CW radar system) according to one embodiment ofthe present invention.

FIG. 28B is a table for additional resistance values for an amplifierboard for a radar system (e.g., a CW radar system) according to oneembodiment of the present invention.

FIG. 28C is a table for additional resistance values for an amplifierboard for a radar system (e.g., a CW radar system) according to oneembodiment of the present invention.

FIG. 29 illustrates an amplifier board for a radar system (e.g., a CWradar system) according to another embodiment of the present invention.

FIG. 30 illustrates an amplifier board for a radar system (e.g., a CWradar system) according to another embodiment of the present invention.

FIG. 31A illustrates the top of an impedance matching board for a radarsystem (e.g., a CW radar system) according to one embodiment of thepresent invention.

FIG. 31B illustrates the schematic of an impedance matching board for aradar system (e.g., a CW radar system) according to one embodiment ofthe present invention.

FIG. 32 illustrates a graphical user interface (GUI) for displayingobjects detected by a radar system (e.g., a CW radar system) accordingto one embodiment of the present invention.

FIG. 33 illustrates a GUI for displaying objects detected by a radarsystem (e.g., a CW radar system) according to one embodiment of thepresent invention.

FIG. 34 illustrates a sonar GUI for a radar system (e.g., a CW radarsystem) according to one embodiment of the present invention.

FIG. 35 illustrates a travel route GUI for a radar system (e.g., a CWradar system) according to one embodiment of the present invention.

FIG. 36A illustrates a two-dimensional (2D) map indicating a log scaleof a normalized energy product for a radar system (e.g., a CW radarsystem) with no detected targets according to one embodiment of thepresent invention.

FIG. 36B illustrates a 2D map indicating a log scale of a normalizedenergy product for a radar system (e.g., a CW radar system) withdetected targets according to another embodiment of the presentinvention.

FIG. 37A illustrates a 2D density and intensity map for a radar system(e.g., a CW radar system) according to one embodiment of the presentinvention.

FIG. 37B illustrates a 2D density map for a radar system (e.g., a CWradar system) according to one embodiment of the present invention.

FIG. 38 illustrates a GUI for displaying energy and frequency dataassociated with a radar system (e.g., a CW radar system) according toone embodiment of the present invention.

FIG. 39 illustrates a GUI for displaying phase detail and power historydata associated with a radar system (e.g., a CW radar system) accordingto one embodiment of the present invention.

FIG. 40 is a schematic diagram of a system of the present invention.

FIG. 41 illustrates an amplifier board for a radar system (e.g., a CWradar system) according to one embodiment of the present invention.

FIG. 42 illustrates an amplifier board schematic for a radar system(e.g., a CW radar system) according to another embodiment of the presentinvention.

FIG. 43 illustrates an amplifier board for a radar system (e.g., a CWradar system) according to yet another embodiment of the presentinvention.

FIG. 44 illustrates an amplifier board for a radar system (e.g., a CWradar system) according to yet another embodiment of the presentinvention.

FIG. 45 illustrates an amplifier board for a radar system (e.g., a CWradar system) according to yet another embodiment of the presentinvention.

FIG. 46 illustrates an amplifier board for a radar system (e.g., a CWradar system) according to yet another embodiment of the presentinvention.

FIG. 47 illustrates one embodiment of a system of the present inventionincluding an active tow fish.

FIG. 48 illustrates one embodiment of a system of the present inventionincluding a remotely operated vehicle (ROV).

FIG. 49 illustrates one embodiment of a system of the present inventionincluding an autonomous underwater vehicle (AUV).

FIG. 50 illustrates one embodiment of a pinpoint localization system(PLS) with 2-axes.

FIG. 51 illustrates one embodiment of a PLS with 3-axes.

FIG. 52 illustrates one embodiment of a sequential transmit and receivesystem.

FIG. 53 illustrates one example of a continuous wave search signal for aPLS.

FIG. 54 illustrates one embodiment with a single Tx antenna withmultiple Rx antennas.

FIG. 55 illustrates one embodiment with multiple Tx antennas andmultiple Rx antennas.

FIG. 56 illustrates one embodiment of multiple Tx antennas and multipleRx antennas with phasing for focus an area of survey.

FIG. 57 illustrates one embodiment of a handheld radar system.

FIG. 58 illustrates one embodiment of a control handle of a handheldradar system.

FIG. 59 illustrates one embodiment of an ROV or AUV mounted radarsystem.

FIG. 60 illustrates one embodiment of an ROV or AUV mounted radar systemwith reduced mechanical noise sources.

FIG. 61 illustrates one embodiment of an ROV or AUV mounted radar systemwith all external noise sources removed.

FIG. 62 illustrates one embodiment of a precision location device fordeep sub-floor search, detection, location, and identification ofsub-surface metals using a stationary radar system.

FIG. 63 illustrates one embodiment of a precision location device fordeep sub-floor search, detection, location, and identification ofsub-surface metals with enhanced geolocation and sensitivity.

FIG. 64A illustrates a partial view of a real-time control andmonitoring GUI.

FIG. 64B illustrates the remaining portion of the real-time control andmonitoring GUI continued from FIG. 64A.

FIG. 64C lists all the labels in FIGS. 64A and 64B.

FIG. 65 illustrates one embodiment of an automatic target cueing mapcreated by the analysis software system.

FIG. 66A illustrates one embodiment of the radar system that uses twoparallel receive arrays to provide real-time determination of targetlocation to left or right of track.

FIG. 66B lists all the labels in FIG. 66A.

FIG. 67A illustrates one embodiment of the radar system that uses threeparallel receive arrays to determine target location left or right ofsurvey track and provide enhanced 3D geolocation and mapping ofsub-ocean floor metals.

FIG. 67B lists all the labels in FIG. 67A.

FIG. 68A illustrates a side view of one embodiment of the radar systemthat uses vertical transmit antennas and horizontal receive antennas toimprove polarization rejection of the direct path signal while providingreal-time location of targets to left or right of survey line.

FIG. 68B illustrates a top view of the embodiment shown in FIG. 68A.

FIG. 68C lists all the labels in FIGS. 68A and 68B.

FIG. 69A illustrates a side view of one embodiment of the radar systemthat uses vertical transmit antennas and horizontal receive antennas toprovide improve polarization rejection of the direct path signal,provide real-time target location to left or right of survey track, andprovide enhanced 3D geolocation and mapping of sub-ocean floor metals.

FIG. 69B illustrates a top view of the embodiment shown in FIG. 69A.

FIG. 69C lists all the labels in FIGS. 69A and 69B.

FIG. 70A illustrates one embodiment with at least one transmitter and atleast one receiver located in a fixed position on the ocean floor.

FIG. 70B lists all the labels in FIG. 70A.

FIG. 71A illustrates one embodiment with multiple transmitter andreceiver antennas deployed in an area to act as a detection fence-line.

FIG. 71B lists all the labels in FIG. 71A.

FIG. 72A illustrates one embodiment with multiple systems interconnectedvia radiofrequency communication.

FIG. 72B lists all the labels in FIG. 72A.

FIG. 73A illustrates one embodiment with a plurality of nodes deployedin a pattern to surveil a specific region.

FIG. 73B lists all the labels in FIG. 73A.

FIG. 74A shows the possible gain states of for an operational amplifierusing 16 resistors in series configuration.

FIG. 74B shows a subset of the possible gains that are selected basedupon linear gain steps.

FIG. 74C shows the error between the actual gain settings and atheoretical perfectly linear distribution of gain settings.

FIG. 74D shows the possible gain settings for an Instrument Amplifierusing a parallel resistor network.

FIG. 74E shows the actual gain setting used which are selected basedupon linear gain steps.

FIG. 74F shows the error between the actual gain values that wereselected and a theoretical perfectly linear distribution of gainsettings.

DETAILED DESCRIPTION

The present invention is generally directed to a continuous-wave (CW)radar system for detecting ferrous and non-ferrous metals in saltwaterenvironments, as well as methods of using the radar system (e.g., the CWradar system) to detect, geolocate in two and/or three dimensions usingabsolute and/or relative coordinate systems, convert geolocation to twoand three dimensional mapping systems, determine an approximate size ofan object, and determine a material composition of the object forferrous and non-ferrous metals in underwater (e.g., saltwater)environments.

In one embodiment, the present invention provides a radar system fordetecting ferrous and non-ferrous metals in an underwater environment,including at least one support vessel, an antenna system including atleast one signal generator, at least one transmitter (Tx) antenna, atleast one receiver (Rx) antenna, and at least one signal processor,wherein the at least one Tx antenna and the at least one Rx antenna arefixed in a cross-polarized orientation with each other or electricallyisolated by distance and/or topography, wherein the at least one Rxantenna is substantially perpendicular to a direction of travel of theat least one support vessel, wherein the at least one signal generatoris operable to emit at least one transmission signal to a target areathrough the at least one Tx antenna, wherein the at least one Rx antennais operable to receive at least one return signal from the target area,wherein the at least one signal processor is operable to analyze the atleast one return signal, wherein the at least one signal processor isoperable to detect and/or locate at least one target object in thetarget area based on the at least one return signal, and wherein theunderwater environment is a saltwater environment. In one embodiment,the system further includes a graphical user interface (GUI), whereinthe GUI is operable to display a visualization of the at least onetarget object in the target area. In one embodiment, the antenna systemincludes a plurality of Rx antennas for each of the at least one Txantennas. In one embodiment, the at least one transmission signal is aplurality of transmission signals, and wherein the plurality oftransmission signals includes at least two different frequencies and/orat least two different power levels. In one embodiment, the at least onesignal processor is operable to identify at least one constructiveinterference zone and at least one destructive interference zone in thetarget area. In one embodiment, the support vessel is an active towfish, a remotely operated vehicle (ROV), or an autonomous underwatervehicle (AUV). In one embodiment, information from the at least onesignal processor is transmitted to land-based and/or water-based systemsvia fiber-optic communication, wired communication, and/or low frequencysub-channel radio frequency (RF) communication. In one embodiment, theat least one signal processor is operable to distinguish betweendifferent types of metal forming the at least one target object. In oneembodiment, the at least one Tx antenna and the at least one Rx antennaincludes a plurality of Tx antennas and a plurality of Rx antennas,wherein the plurality of Tx antennas and the plurality of Rx antennasare interlinked via fiber-optic communication, wired communication,and/or low frequency sub-channel radio frequency (RF) communication. Inone embodiment, the at least one Tx antenna and the at least one Rxantenna includes a plurality of Tx antennas and a plurality of Rxantennas, wherein the plurality of Tx antennas and the plurality of Rxantennas are arranged in a pattern to form a radio frequency (RF) fence,and wherein the radar system is operable to identify movement across theRF fence. In one embodiment, the at least one Rx antenna includes aplurality of Rx antennas, wherein the plurality of Rx antennas isarranged in at least two parallel lines. In one embodiment, the radarsystem is operable to identify a location and/or a travel direction forsurface vessels, sub-surface vessels, and/or divers in the target area.In one embodiment, the system further includes at least one amplifierboard, wherein the at least one Rx antenna is connected to the at leastone amplifier board using at least one discrete resistor networkarranged in a parallel and/or series configuration, and wherein at leastone switch and/or at least one digitally controlled relay is operable toadjust gain on at least one amplifier on the at least one amplifierboard. In one embodiment, the system further includes at least oneamplifier board, wherein the at least one amplifier board includes atleast one narrow band filter to allow at least one high powerout-of-band signal to be transmitted without interfering with receptionof at least one in-band signal.

In another embodiment, the present invention provides a radar system fordetecting ferrous and non-ferrous metals in an underwater environment,including at least one support vessel, an antenna system including atleast one signal generator, at least one transmitter (Tx) antenna, atleast one receiver (Rx) antenna, and at least one signal processor,wherein the at least one Tx antenna and the at least one Rx antenna arefixed in a cross-polarized orientation with each other or electricallyisolated by distance and/or topography, wherein the at least one Rxantenna is substantially perpendicular to a direction of travel of theat least one support vessel, and a geolocation system, wherein the atleast one signal generator is operable to emit at least one transmissionsignal to a target area through the at least one Tx antenna, wherein theat least one Rx antenna is operable to receive at least one returnsignal from the target area, wherein the at least one signal processoris operable to analyze the at least one return signal, wherein the atleast one signal processor is operable to detect and/or locate at leastone target object in the target area based on the at least one returnsignal, wherein the at least one signal processor is operable todetermine a relative geolocation and/or an absolute geolocation of theat least one target object using the geolocation system, and wherein theunderwater environment is a saltwater environment. In one embodiment,the geolocation system includes a plurality of signal reflectors in theunderwater environment. In one embodiment, the geolocation systemincludes at least one global positioning system (GPS) module.

In yet another embodiment, the present invention provides a method fordetecting ferrous and non-ferrous metals in an underwater environment,including at least one support vessel traversing a target area, at leastone signal generator emitting at least one transmission signal to thetarget area through at least one transmitter (Tx) antenna, at least onereceiver (Rx) antenna receiving at least one return signal from thetarget area, at least one signal processor analyzing the at least onereturn signal, and the at least one signal processor detecting and/orlocating at least one target object in the target area based on the atleast one return signal, wherein the at least one Tx antenna and the atleast one Rx antenna are fixed in a cross-polarized orientation witheach other, wherein the at least one Rx antenna is substantiallyperpendicular to a direction of travel of the at least one supportvessel, and wherein the underwater environment is a saltwaterenvironment. In one embodiment, the method further includes the supportvessel traversing at least one portion of the target area multipletimes. In one embodiment, the at least one transmission signal is aplurality of transmission signals, wherein the plurality of transmissionsignals includes at least two frequencies and/or at least two powerlevels. In one embodiment, the method further includes the at least onesignal processor identifying at least one constructive interference zoneand at least one destructive interference zone in the target area. Inone embodiment, the method further includes the at least one signalprocessor identifying metals comprising the at least one target object.In one embodiment, the method further includes adjusting gain of atleast one amplifier on at least one amplifier board using at least oneswitch and/or at least one digitally controlled relay, wherein the atleast one Rx antenna is connected to the at least one amplifier boardusing at least one discrete resistor network arranged in a paralleland/or series configuration. In one embodiment, the method furtherincludes the at least one signal processor determining athree-dimensional (3D) distribution of the at least one target object onand/or below a floor of the underwater environment.

None of the prior art discloses the use of extremely-low frequency (ELF)electromagnetic (EM) waves in saltwater to pinpoint and/or locateferrous and non-ferrous metals.

Current underwater detection and surveying technologies make use ofmagnetometers which are only able to measure magnetism in ferrousmaterials, such as iron or steel. Magnetometers are unable to detectnon-ferrous metals such as gold, silver, copper, brass, bronze,aluminum, molybdenum, zinc, or lead. In addition, magnetometers onlydetect the strength, or relative change of the Earth’s magnetic field ata particular location, and are strictly passive sensors. Thus,magnetometers only use the natural, surrounding magnetism of an object,relying solely on the Earth’s fixed magnetic output as the transmitter(Tx). In such a system, only the magnetometer as the receiver (Rx)portion can be modified or manipulated. Moreover, magnetometers have afixed range based on receiver sensitivity which results in a minimaldetection range for ferrous materials.

While sub-bottom sonar, side scanning sonar, dual band metal detectors,ground penetrating radar (GPR), and pulsed-wave (PW) radar techniquesare also available, these detection technologies are subject to faultsand limitations that make their usage in saltwater environmentsimpractical.

Sub-bottom sonar systems are able to penetrate the ocean floor, butcannot identify, locate, or differentiate between sedimentary material,ferrous material, and non-ferrous material. These systems can onlydetect “acoustic” impedance, which provides for determining changes indensity from one stratigraphic layer to another stratigraphic layer ofthe subsurface geology. Acoustic impedance corresponds to a physical“pressure” wave (e.g., sound, physical vibrations, earthquakes, etc.),while “electrical” impedance corresponds to an electromagnetic wave(e.g., signals from radio, cell phones, microwaves, light, etc.).Typically, sub-bottom sonar systems operate in the acoustic range of5-50 kilohertz (kHz). While lower frequencies penetrate deeper into mudand silt, these systems lack the ability to provide real detail of thedetected layers. In contrast, higher frequencies provide minor surfacelayer detail, but lack the ability to penetrate sand, mud, or silt.

Side-scanning sonar is typically used to create a map of the oceanbottom. However, much like sub-bottom sonar, side-scanning sonar lacksthe ability to penetrate into the surface of the ocean bottom. Thedevices utilized for side-scanning sonar are also acoustic-only devices.

Dual band metal detectors are also used in underwater salvaging. Thesesystems are active systems and are able to identify ferrous andnon-ferrous metals using dual frequency differences to determine metaltypes (e.g., ferrous vs. non-ferrous). Dual band metal detectors operatein the 5-100 kilohertz (kHz) range and are typically able to penetratebetween 7.6 cm (3 inches) to 45.7 cm (18 inches) of sand, saltwater,soil, etc. In addition, dual band metal detectors are restricted tosearching an area directly under the detector unit’s coil diameter,which is typically less than 30.5 cm (12 inches) in diameter.

Ground penetrating radar (GPR) systems are used only in airenvironments. The frequency of GPR falls between 10-3000 megahertz(MHz). Even if a GPR system was encapsulated for ocean use, the radarenergy would immediately be absorbed on contact with saltwater and itseffective range would be less than 2.54 cm (1 inch). High frequency,commercial, hand-held metal detectors used on the land have the abilityto not only detect metal objects (typically < 1.8 m (6 ft) away), butare also able to classify what type of metal the object is made of(e.g., gold, silver, iron, etc.). This is accomplished through thedifferences between the multiple radar bands. In multiple signalsystems, signals reflect off of the metal, but based on the metalmaterial, the strength and phase of return between the frequencies isdifferent. However, the frequencies of these commercial metal detectorsdo not transmit far enough in saltwater environments before beingcompletely absorbed by the water and hence are operationallyineffective.

Pulsed-wave (PW) radar systems transmit electromagnetic (EM) wavesduring a time duration, or pulse width. During this process, thereceiver is isolated from the antenna in order to protect the receiver’ssensitive components from a transmitter’s high-power EM waves. Noreceived signals are operable to be detected during this time.

The faults and limitations of the previously mentioned detection andsensor technologies have led to the present invention: a continuous-wave(CW) radar system for detecting ferrous and non-ferrous objects insaltwater environments. Such a radar system combines all of the positiveattributes of current sensor and detection technologies with none of thelimitations or faults. Instead of relying on “acoustic” waves, thesystem uses “electromagnetic” waves, but at frequencies which allow forgreater penetration than even the most sophisticated sub-bottom sonarsystems.

In one embodiment, the radar system (e.g., the CW radar system)generates electromagnetic (EM) waves and uses those EM waves to performfunctions including, but not limited to, detection, location,classification, and identification of objects of interest. Such objectsinclude, but are not limited to, all types of ferrous and non-ferrousmetals, as well as changing material boundary layers (e.g., soil towater, sand to mud, rock to organic materials, etc.). In one embodiment,the EM waves used are between 1 Hz and 1 MHz. In one embodiment, theradar system (e.g., the CW radar system) is operable to detect andrecord all frequencies below 1 MHz. In one embodiment, the radar system(e.g., the CW radar system) generates ELF EM waves. In one embodiment,the ELF EM waves used are between 100 Hz and 3000 Hz. In one embodiment,the radar system (e.g., the CW radar system) is operable to detect andrecord all frequencies below approximately 3000 Hz. Thus, the ELF EMwaves are operable to propagate through water, soil, sand, rock, and/ormetals. A portion of the ELF EM waves are reflected off of thickermetals and boundary layers, which are used to perform functionsincluding, but not limited to, detection, location, analysis, mapping,and/or classification of objects. This entire process is performed usingshort, manageable antennas which are operable to transmit and receivethe same ELF EM waves or signals. Thus, the present invention isoperable to identify both ferrous and non-ferrous metals.

In one embodiment, the radar system (e.g., the CW radar system) of thepresent invention makes use of a multi-band system capable of operatingat simultaneous frequencies in order to decrease location error andprovide the ability to specifically identify the type of metalassociated with an object and/or target during operations.

A key element of this system is the environment it functions in:saltwater. Saltwater is conductive and distributed equally around thesystem’s sensors. The saltwater becomes a barrier to transmission, dueto absorption, but simultaneously acts as a filter to keep the detectionranges local to the sensor. Without a saltwater environment, thetransmission ranges measure in kilometers instead of meters. Allconductive surfaces within a few kilometers would create a return signaland greatly reduce the ability to locate a specific target, local to thesensors. Saltwater changes the effective wavelength from potentiallythousands of kilometers to less than 100 meters, enabling detection oftargets, as well as localization of objects around the system’s sensorsfrom a few meters to a few hundred meters, based on Tx signal strengthand Rx sensitivity. In one embodiment, the system is operable to handlevariations in salinity within at least an 80.5 km (50 mile) radiuswithout further adjustment. In another embodiment, the system isoperable to be recalibrated at startup and/or when the saltwaterenvironment changes to accommodate different levels of salinity. In oneembodiment, the system is operable to detect targets and/or objects inbrackish water.

The radar system (e.g., the CW radar system) is operable to function indeep saltwater environments, from tens of feet to tens of thousands offeet. Moreover, the design of the radar system (e.g., the CW radarsystem) of the present invention prevents saltwater from contaminatingthe towing device(s) connected to a collecting and/or towing vehicle.The radar system (e.g., the CW radar system) is capable of determiningabsolute object and/or target geolocation to within < 4 meters (m)circular error probable (CEP) of accuracy. The radar system (e.g., theCW radar system) is also capable of providing object and/or targetgeolocation within < 2 m CEP of accuracy using a relative positioningsystem. In one embodiment, relative positioning is determined throughthe use of a GPS receiver. In another embodiment, the relativepositioning of detected targets is determined with respect to knownmetal targets or markers placed within the field of search.

Referring now to the drawings in general, the illustrations are for thepurpose of describing one or more preferred embodiments of the inventionand are not intended to limit the invention thereto.

The continuous-wave (CW) radar system of the present invention utilizesa combination of transmitter (Tx) and receiver (Rx) antennas. By usingmultiple Rx antennas, the system is able to reject clutter and providemore accurate localization of objects.

FIG. 1A illustrates a block diagram of a continuous-wave (CW) radarsystem according to one embodiment of the present invention. Thecomponents include, but are not limited to, a transmitter computer, areceiver computer, at least two amplifiers, a storage component, atleast two impedance matching hardware components coupled to the at leasttwo amplifiers, a continuous wave sensor head (the submerged, towedstructure comprising the Transmitter (Tx), Receiver (Rx) antennas, downplane, horizontal stabilizer, floatation elements, and structuralsupport elements), a tow point, a Tx communications cable, a Rxcommunications cable. The continuous wave sensor head is comprised of atleast one transmitter (Tx) antenna and at least two receiver (Rx)antennas. The submersion of the Tx and Rx antennas in a saltwaterenvironment modifies the relative Tx and Rx wavelengths from thousandsof kilometers to less than a few hundred of meters range. This enablesthe use of electrically short dipole antennas to collect enough energy,at the Rx antennas, to detect, locate, and/or identify all types offerrous and non-ferrous metals.

FIG. 1B illustrates a pipe frame for a radar system (e.g., a CW radarsystem) according to another embodiment of the present invention. Theradar system (e.g., the CW radar system) is comprised of a multitude ofpiping, operable to house at least one Tx antenna and at least two Rxantennas.

FIG. 1C illustrates a radar system (e.g., a CW radar system) accordingto yet another embodiment of the present invention. The radar system(e.g., the CW radar system) is comprised of components including, butnot limited to, a tow point, a Rx/Tx communications cable, a down plane,a horizontal stabilizer, at least one Tx antenna, and/or at least two Rxantennas. The tow point is positioned to maximize the stability of theradar system (e.g., the CW radar system) while it is being towed from atowing vessel. In one embodiment, the towing vessel is a watercraft,including but not limited to a boat, ship, JET SKI, or submarine. Inanother embodiment, the towing vessel is an underwater Remotely OperatedVehicle (ROV). In another embodiment, the towing vessel is an AutonomousUnderwater Vehicle (AUV). The tow point also helps keep the tow cableseparate from the data cable. The data cable enters the radar system(e.g., the CW radar system) above and behind the tow point on top of theradar system (e.g., the CW radar system). The data cable has multipleelectrically shielded wires running throughout the structure to each ofthe six antennas, four Rx antennas and two Tx antennas. Furthermore, thepath of the data cable throughout the radar system (e.g., the CW radarsystem) is also important, as the cable(s) are run in order to maximizetheir individual cross polarization to the Tx antennas. By positioningthe Tx antennas at a 90-degree angle in relation to the Rx antennas,this prevents the Rx antenna’s wiring from coming into contact with theTx antenna output pattern, further reducing the crosstalk from the Txantennas into the Rx antenna data cable(s). The 90-degree angle betweenTx and Rx antennas also provides for the majority of the direct pathattenuation through the use of the polarization properties of dipoleantennas. Without this attenuation, signal from the Tx antenna wouldsaturate the Rx antenna and any returning signal from a target would belost due to the much, much stronger direct path signal.

FIG. 1D illustrates the radar system (e.g., the CW radar system) of FIG.1C showing the location of antennas in the piping according to anotherembodiment of the present invention. The radar system (e.g., the CWradar system) is comprised of components including, but not limited to,at least two bow Rx antennas, at least two Tx antennas placedapproximately at the center of the radar system (e.g., the CW radarsystem), and at least two aft Rx antennas. In one embodiment, the atleast two Tx antennas are positioned near a horizontal stabilizer forthe radar system (e.g., the CW radar system). In one embodiment, the Txand Rx antennas are dipole antennas. When two dipole antennas are placedin close proximity to one another, this sets up a transformer-likecondition, resulting in a loss of power to the radar system if eachantenna is too close to the other. As in a transformer, energy from oneTx antenna is absorbed by any adjacent Tx antenna. This results in adirect loss of usable power and requires the system to also prevent thislost energy/power from feeding back in to either Tx antenna’s circuitry.In order to minimize these effects, the radar system (e.g., the CW radarsystem) of the present invention has been constructed with a functionaldistance built into the structure, holding the radar antennas separate.This functional distance is a function of how much transmitted energyloss is acceptable for the radar system (e.g., the CW radar system) andthe specific transmitted frequencies being used. In one embodiment, therange for acceptable energy loss is between 5-20%. In one embodiment,the antennas are placed between approximately 22.9-61.0 cm (9-24 inches)away from each other to maintain acceptable energy loss wherein thedistance is inversely proportional to the amount of energy loss. Wherethe Rx antennas are also dipole antennas, the Tx antennas must be angled90-degrees or near-90-degrees with respect to the Rx antennas in orderto maximize the benefits of cross polarization. In another embodiment,the Tx and Rx antennas are short dipole antennas. In another embodiment,the Tx and Rx antennas are half-wave dipole antennas. In anotherembodiment, the Tx and Rx antennas are folded dipole antennas. In yetanother embodiment, the Tx and Rx antennas are bow-tie dipole antennas.In yet another embodiment, the Tx and Rx antennas are cage dipoleantennas. In yet another embodiment, the Tx and Rx antennas are halodipole antennas. In yet another embodiment, the Tx and Rx antennas areturnstile dipole antennas. In yet another embodiment, the Tx and Rxantennas are sloper dipole antennas. In yet another embodiment, the Txand Rx antennas are inverted “V” dipole antennas. In yet anotherembodiment, the Tx and Rx antennas are G5RV dipole antennas. In yetanother embodiment, the Tx and Rx antennas are not dipole antennas.

In one embodiment, a Tx antenna is placed in one of two center pipes andthe corresponding Rx antenna pair(s) are perpendicular to the Txantenna, forward and aft. Each Rx antenna is placed approximately 1-3meters from the Tx antenna. The Rx antenna pair(s) are alwaysperpendicular or substantially perpendicular to the Tx antenna in orderto take advantage of the noise cancellation provided by the polarizationcharacteristics of the antennas. In one embodiment, one Tx antennaeffectively has four Rx antennas, two forward and two aft, with each Rxantenna spaced approximately 1-2 meters away from the Tx antenna. In oneembodiment, the Tx and Rx antennas are spaced approximately 152.4 cm (60inches) apart from each other. In one embodiment, the Tx and Rx antennastructures are approximately 4.4 m (14.5 feet) long in total when usinga multiband system.

The addition of multiple Rx antennas facilitates the detection of signalstrength and phase changes between the Rx antennas. Each Rx antennaremains perpendicular or substantially perpendicular to the surface ofthe water, while the Tx antenna(s) remain parallel or substantiallyparallel to the water’s surface. This keeps the Tx and Rx antennas atright angles to each other, preventing self-jamming and shielding the Rxantennas from the water’s surface reflection. Thus, this orientationfunctions to prevent self-jamming and reduce the surface bounce energyfrom the Tx into the Rx antenna(s).

In one embodiment, the radar system (e.g., the CW radar system) includesa third Tx/Rx antenna combination. In another embodiment, the radarsystem (e.g., the CW radar system) includes a fourth Tx/Rx antennacombination. In yet another embodiment, the radar system (e.g., the CWradar system) includes more than four Tx/Rx antenna combinations. In oneembodiment, additional cross pipes are included in the design of thepiping frame, thereby providing for the radar system (e.g., the CW radarsystem) to accommodate more bands while only increasing the overalllength of the piping frame of the radar system (e.g., the CW radarsystem) for each added band. All portions/elements of the underwaterstructure housing the cables, Tx/Rx antennas, and connectors are madefrom dielectric or non-metallic, non-conducting material.

The entire CW radar system is towed from a single tow point, maximizingstability while towing and keeping the towing cable separate from a datacable. The data cable enters the radar system (e.g., the CW radarsystem) above and behind the tow point. The data cable has multipleelectrically shielded wires running throughout the structure to each ofthe Tx and Rx antennas. Data cables are positioned to maximize theirindividual cross-polarization while avoiding exposure to the Txantenna(s) output pattern, reducing crosstalk from the Tx and Rx antennadata cables.

The structure of the radar system (e.g., the CW radar system) of thepresent invention further minimizes issues with vibration. Mechanicalvibrations induce a Doppler response into the processed data, directlycontributing to decrease in Signal to Noise Ratio (SNR) in the system.In one embodiment, the ballast between the panels is constructed ofhigh-density foam with a crush depth of more than 1219 m (4000 feet)deep. This enables the system to remain buoyant and keeps panels of thesystem from vibrating under towing conditions. The panels also serve tokeep the pipes and structures holding the cables and antennas rigid.Thus, the combination of the panels and high-density foam reducesoverall system vibration when being towed. In embodiment, the system istowed at speeds up to approximately 12 knots (kts). In anotherembodiment, the system is towed at a speed greater than 12 kts.

FIG. 1E illustrates a side view of a radar system (e.g., a CW radarsystem) according to one embodiment of the present invention. A towpoint is positioned at one end of the radar system (e.g., the CW radarsystem), enabling a towing vessel to attach to the radar system (e.g.,the CW radar system). The radar system (e.g., the CW radar system) alsoincludes a buoyancy tank, enabling the radar system (e.g., the CW radarsystem) to remain afloat on the surface of a body of water. In oneembodiment, the radar system (e.g., the CW radar system) is connected tothe towing vessel via a tow cable and a data cable. In one embodiment,the radar system (e.g., the CW radar system) is connected to the towingvessel via a dinghy, where the dinghy is connected to the towing vesselvia a data cable and tow cable, and the dinghy connects to the radarsystem (e.g., the CW radar system) using the data cable and/or towcable.

FIG. 1F illustrates a top view of a radar system (e.g., a CW radarsystem) according to one embodiment of the present invention. The radarsystem (e.g., the CW radar system) includes at least one down plane,operable to adjust the angle of the radar system (e.g., the CW radarsystem) as it travels along the surface of a body of water, and at leastone buoyancy tank.

FIG. 1G illustrates a nose-on view of a radar system (e.g., a CW radarsystem) according to one embodiment of the present invention.

FIG. 1H illustrates a side view of a radar system (e.g., a CW radarsystem) according to one embodiment of the present invention. The systemhas a movable dive plane (seen on the lower front corner of the sensorhead). The design has provision for adjustable floatation (yellowcylinders along the top of the sensor head) and for adjustable ballast(yellow cylinders along the bottom of the sensor head). The design shownin FIG. 1H includes provision for up to three Tx antennas and sixreceive antennas (three forward and three aft of the Tx antennas). Inone embodiment, the system includes additional antennas. For example,and not limitation, in one embodiment, the system includes four Txantennas and eight Rx antennas. In a preferred embodiment, the antennasare mounted in removable cartridges, which advantageously allow for easyrepair and/or replacement. In one embodiment, the antenna cartridges areoperable to be removed and replaced with antennas with differentcapabilities (e.g., frequency, power, type, depth rating, etc.) whilethe system is at sea or on land. FIG. 1I shows the radar system once theside panels have been installed.

In one embodiment, the radar system (e.g., the CW radar system) includesa down plane. The down plane is placed forward of the center of balanceof the radar system (e.g., the CW radar system). This positioning, inconjunction with the two point and horizontal stabilizer, provides abalanced, smooth towing operation. The down plane is sized and angled toprovide precise underwater depths for the radar system (e.g., the CWradar system) when being towed at peak, desired collection speeds. Inone embodiment, the peak towing speed for collection is approximately2-8 kts. The depth of the radar system (e.g., the CW radar system)’skeel from the ocean surface is a function of tow cable length for a setcollection speed. In one embodiment, the down plane is a fiberglass downplane. In one embodiment, the down plane is made of polyvinyl chloride(PVC). In another embodiment, the down plane is made of fiberglasscomposite. In another embodiment, the down plane is made of anon-metallic, non-conducting, dielectric material. In one embodiment,the down plane is actively adjustable. Using an actively adjustable downplane enables the radar system (e.g., the CW radar system) to operate atgreater depths. In another embodiment, the down plane is coupled with asonar reflector system on the radar system (e.g., the CW radar system)in order to precisely locate targets underwater. This coupling of thedown plane with the sonar reflector system increases the geolocationalaccuracy of the radar system (e.g., the CW radar system) duringsurveying operations. In one embodiment, the sonar reflector is a cornerreflector that reflects a sonar acoustic signal. In one embodiment, thesonar reflector signal is used by the towing vessel to determine thelocation and depth of the radar system (e.g., the CW radar system) as itis being towed. In one embodiment, the sonar reflector is operable tolocate the corners of the radar system (e.g., the CW radar system) as itis being towed. In one embodiment, there is at least one transponder oneach side of the towing vessel. The transponders each emit signals ofdifferent frequencies. The location and depth of the radar system (e.g.,the CW radar system) is calculated using the combined stereo vision ofthe at least one transponder on each side of the towing vessel. In oneembodiment, the system is operable to generate a 3D image of the radarsystem (e.g., the CW radar system) as it is being towed with geolocationaccuracy of the radar system (e.g., the CW radar system) within 3 m (10ft).

In one embodiment, the radar system (e.g., the CW radar system) of thepresent invention further includes a towed floatation device attached tothe radar system (e.g., the CW radar system). In one embodiment, thetowed flotation device is a dinghy. The towed floatation device cushionsthe radar system (e.g., the CW radar system) against waves, reducingsudden jerking motions encountered while towing and vibrational noise.In one embodiment, the towed floatation device also carries anadditional GPS receiver that helps to triangulate the location of theunderwater sensor-head during surveying operations. The combination ofall GPS receiver(s) on the towing vessel and the towed floatation devicetogether provides a <2 m accuracy of the underwater sensor-head.

In one embodiment, the sensor-head is coupled with an active tow fish tocontrol the height of the sensor above the ocean floor. Advantageously,this allows the system to be used in a wide variety of ocean floorterrains. In one embodiment, the sensor head of the tow fish isconnected to the surface with a single fiber optic cable includingpower, replacing a plurality of cables with the single fiber optic cableincluding power. Preliminary analog processing of signals is conductedon the tow fish and then transmitted to the surface as a digital stream.Advantageously, this significantly reduces the number of cables and,therefore, the size and weight of the cables needed to operate thesystem. This also dramatically reduces the cost of cabling for thesystem. In one embodiment, from the tow fish back, individual wires arehoused in an integrated cable and run to the sensor head where the wirefor each antenna is broken out, providing the transmit signals andreturning the received signals. Control of the sensor is providedremotely from the surface via the fiber optic cable and managed by thetow fish electronics.

The system is operable to provide insight into the ocean floor andsub-floor environment. In one embodiment, the system further includes atleast one additional survey technology. In one embodiment, the tow fishincludes a geo-positioning transponder to allow the precise location ofany return. In one embodiment, the system also includes dualmagnetometers (one on either side), sub-bottom profile sonar, and/orside-scan sonar. The radar system (e.g., the CW radar system) and the atleast one additional survey technology are georeferenced and temporallyaligned to allow multi-sensor fusion of a complete data set.

FIG. 47 illustrates one embodiment of a system of the present invention.The system 100 includes a vessel 110 connected to an active tow fish 120via a fiber optic cable including power 112. The active tow fish 120includes side-scan sonar 122, at least one magnetometer 124 (e.g., twomagnetometers), a sub-bottom profiler 126, electronics for the radarsystem (e.g., the CW radar system) 128, and an active transponder 130.The active tow fish 120 further includes a dive plane 132 and a rudder134. The active tow fish 120 is connected to the radar system (e.g., theCW radar system) 140 via a cable 138. In one embodiment, the cable 138from the active tow fish 120 to the radar system 140 is a singleintegrated cable carrying power to at least one Low Noise Amplifier(LNA) on each receive antenna and signal from the receive antennas afteramplification by the at least one LNA. The cable 138 also carries thetransmitter signal to the transmitter antennas as well as returningmonitor signal necessary to prevent damage to the transmitter antennas.In one embodiment, the side-scan sonar is a commercial off-the-shelfunit. The specific model and capabilities of the side-scan sonar areoperable to be selected based upon requirements of the survey. In oneembodiment, the magnetometers are operable to be commercialoff-the-shelf units. The specific model and capabilities of themagnetometer are operable to be selected based upon the requirements ofthe survey. In one embodiment, the sub-bottom profiler is a commercialoff-the-shelf unit. The specific model and capabilities of thesub-bottom profiler are operable to be selected based upon therequirements of the survey.

In one embodiment, the receivers have impedance matching circuitry andat least one Low Noise Amplifier (LNA) embedded with the receiverantennas. The at least one LNA is operable to amplify the very smallsignal of the receiver antennas and convert the signal such that thesignal is operable to be transmitted over coaxial cable. The at leastone LNA is attached to the antenna through impedance matching circuitryto maximize the signal received and help reduce out of band noise.

In one embodiment, the receiver antennas include an impedance matchingcircuit combined with a BALUN to convert a balanced signal of theantenna to an unbalanced signal of the coaxial cable.

In one embodiment, the impedance matching circuit and one or more of theat least one LNA are removed from the antenna and placed along the towcable to remove it from close proximity to the antenna and possibleinterference with the operation of the antenna. A twisted pair cable ofset length is run between the impedance matching circuit to allow for aproper impedance match to be implemented.

In one embodiment, the transmitter signals are sent via coaxial cable tomaximize the signal available to the antenna and make the antennaimpedance matching independent to the length of the cable. A shieldedtwisted pair wire is also run with the coaxial cable. The shieldedtwisted pair is used to carry a monitoring signal back to the controlcomputer to ensure the antennas are not damaged by too strong of atransmitter signal. The transmitter signal in the coaxial cable isconverted from an unbalanced signal in the coaxial cable to a balancedsignal required by the antenna using a BALUN which is encapsulated inthe antenna housing along with the necessary impedance matchingcircuitry.

In one embodiment, the impedance matching circuit and BALUN for thetransmit antenna is removed from the antenna housing and placed alongthe tow cable. A shielded twisted pair cable is run from the impedancematching circuit to the transmitter antennas.

In one embodiment, the cables to the receive antennas are twisted pairand go directly from the antenna feeds to the receiver digitizercircuitry which contain an impedance matching circuit. The impedancematching circuit ensures the receive signal is maximized for theamplifier and filter stage that precede the digitizer. Any significantchange in cable length requires the impedance matching circuit to bemodified to adjust to the changed system impedance. The advantage of thetwisted pair is the removal of one or more of the at least one LNA or aBALUN at the receive antenna.

In one embodiment, the cables to the transmit antennas are shieldedtwisted pair and go directly to the antenna feeds. The shielded twistedpair go through an impedance matching circuit which also has monitoringcircuitry to protect the transmit antennas from damage. The impedancematching circuit is positioned between the power amplifier and thetransmit antennas. In the event the cable lengths are changedsignificantly, the impedance matching circuitry must be adapted to thenew system impedance.

Alternatively, the tow fish is replaced with a remotely operated vehicle(ROV). FIG. 48 illustrates another embodiment of a system of the presentinvention. The system 200 includes a vessel 110 connected to an ROV 220via an ROV tether 212. The ROV 220 includes side-scan sonar 222, atleast one magnetometer 224 (e.g., two magnetometers), a sub-bottomprofiler 226, electronics for the radar system (e.g., the CW radarsystem) 228, and an active transponder 230. The ROV 220 further includesa dive plane 232, a rudder 234, and a propulsion system 236. The ROV 220is connected to the radar system (e.g., the CW radar system) 140 via acable 238. The active tow fish and the ROV have similar cables, but thedrive forces of the systems are different. The active tow fish has nopropulsion and must be towed. The ROV has its own propulsion, but it iscontrolled from the surface. Advantageously, this makes the ROV moremaneuverable and consistent in following desired survey lines. In oneembodiment, the ROV tether has the same fiber optic as the tow fish, buttypically the power supply from the surface is 100x greater in order todrive the propulsion units on the ROV. Thus, the active tow fish cableis lighter and less expensive.

In yet another embodiment, the tow fish is replaced with an autonomousunderwater vehicle (AUV). FIG. 49 illustrates yet another embodiment ofa system of the present invention. The system 300 includes a vessel 110in communication with an AUV 320. The AUV 320 includes side-scan sonar322, at least one magnetometer 324 (e.g., two magnetometers), asub-bottom profiler 326, electronics for the radar system (e.g., the CWradar system) 328, and an active transponder 330. The AUV 320 furtherincludes a dive plane 332, a rudder 334, and a propulsion system 336.The AUV 320 is connected to the radar system (e.g., the CW radar system)140 via a cable 338. The AUV has propulsion and autonomous control ofnavigation and mission profile.

In one embodiment, the radar system (e.g., the CW radar system) isplaced on the keel of a smooth, structurally simple and highly shieldedROV or AUV. The body of the ROV or AUV changes the transmitted andreceived signals and impacts the electrical isolation of the receivers.However, these effects are operable to be calibrated out, with thesystem remaining able to perform. In one embodiment, the system iscalibrated by placing a series of known controlled targets in awell-documented and/or a pristine location where either all theuncontrolled metal objects in the area are known or simply do not exist.The known controlled targets (i.e., calibration targets) are introducedto the area and verified by an existing radar system. Next, the ROV orthe AUV equipped with the radar system surveys the area and thedifferences between the existing radar system and the ROV/AUV radarsystem are calculated such that the effects of the ROV/AUV body areoperable to be removed from the data during future surveys.

In addition, the overall distance between the radar system (e.g., the CWradar system) of the present invention and a towing vessel is ofcritical importance. The engines, hull structures, electronics, aluminumsuperstructures, screws, and other vessel or tow components are operableto create a target that is detected by the radar system (e.g., the CWradar system). In one embodiment, the radar system (e.g., the CW radarsystem) is towed from a vessel between approximately 61 m (200 feet(ft)) to 152.4 m (500 ft) behind the vessel. In one embodiment, theradar system (e.g., the CW radar system) is attached to a dinghy, wherethe distance between the towing vessel and the dinghy is betweenapproximately 30.5 m (100 ft) to 91.4 m (300 ft) and the distance fromthe radar system (e.g., the CW radar system) and the dinghy isapproximately 15.2 m (50 ft) to 121.9 m (400 ft). In another embodiment,the dinghy is more than 91.4 m (300 ft) away from the towing vessel andthe radar system (e.g., the CW radar system) is more than 121.9 m (400ft) from the dinghy. In one embodiment, the towing vessel is awatercraft (boat, ship, JET SKI, submarine, etc.). In one embodiment,the towing vessel is an underwater Remotely Operated Vehicle (ROV). Inone embodiment, the towing vessel is an Autonomous Underwater Vehicle(AUV). In one embodiment, the dinghy is replaced with a dynamic winchsystem onboard the towing vessel. The depth of the sensor-head is thendetermined by the distance of the sensor-head behind the towing vessel.The sensor-head distance from the towing vessel is lengthened orshortened to increase or decrease the sensor-head depth. In oneembodiment, the sensor head depth is adjustable from anywhere betweenabout 30.48 m (100 ft) and about 3,048 m (10,000 ft) depending only onthe capabilities of the support vessel. Below about 3,048 m (10,000 ft),it is rare for winch-based systems to be used. Typically, somewhereafter about 304.8 m (1000 ft), ROV and AUV based systems dominate.

The radar system (e.g., the CW radar system) is capable of transmittingmultiple, simultaneous frequencies. In one embodiment, the radar system(e.g., the CW radar system) transmits multiple simultaneous frequenciesup to approximately 5000 Hz. The radar system (e.g., the CW radarsystem) is compatible with higher frequencies. In one embodiment, theradar system (e.g., the CW radar system) is a dual-band system thatoperates using two separate radars in the same sensor head, enabling thetransmission of multiple frequencies from multiple radarssimultaneously. By using multiple frequencies, the radar system (e.g.,the CW radar system) has increased 3-Dimensional (3D) target geolocationfunctionality and is operable to more efficiently classify surveyedobjects and/or target materials and detect objects and/or targetsthrough solid surfaces, the solid surfaces including but not limited to,soil, sand, reef, mud, and/or iron/steel (e.g., thin iron/steel). In oneembodiment, this dual-band system is comprised of at least one Txantenna and at least two Rx antennas. In one embodiment, this dual-bandsystem is comprised of at least two or more Tx antennas and at least twoor more Rx antennas. In one embodiment, geolocation is achieved with aset of global positioning system (GPS) coordinates. In one embodiment,geolocation is based on a differential GPS system. In one embodiment,the radar system (e.g., the CW radar system) uses GPS receivers on landand/or GPS receivers at anchor points in the underwater environment toimprove the accuracy of the GPS geolocation using differential GPS. Inone embodiment, the radar system (e.g., the CW radar system) includes aplurality of GPS receivers located on the towing vessel and on the towedfloatation device to improve the accuracy of geolocation. In oneembodiment, geolocation is based on a localized or relative coordinatesystem.

In one embodiment, geolocation is based on a relative coordinate systemwherein the relative coordinate system is defined by metal targetsand/or reflectors placed under or on the water surface and in the surveyfield prior to/or during survey operations. In one embodiment, the metaltargets are aluminum. In one embodiment, the metal targets are roundedso as not to skew the directions of the signals that they reflect. Inone embodiment, the metal targets are used for relative geolocationwithin 1-2 m of a target and/or object. All objects discovered from theradar system (e.g., the CW radar system) are then referenced relative tothe metal targets and/or reflectors that were placed into the surveyfield. In one embodiment, geolocation is based on a relative coordinatesystem using active transmitters placed under or on the water surfaceand in the survey field prior to/or during survey operations. Allobjects discovered from the radar system (e.g., the CW radar system) arethen referenced relative to the active transmitters that were placedinto the survey field. In another embodiment, the GPS coordinate systemis used to locate the metal targets, active transmitters, and/orreflectors used to define the relative coordinate system. In oneembodiment, a combination of GPS coordinates and relative coordinatesare used to geolocate the objects and/or targets in the target surveyarea.

By using a dual-band system, the radar system (e.g., the CW radarsystem) is able to transmit a signal from any Tx antenna. Additionally,the radar system (e.g., the CW radar system) is further able to transmitmany signals, simultaneously, within a specific band. For example, inone embodiment, the radar system (e.g., the CW radar system) is able totransmit multiple signals simultaneously within a frequency band up toapproximately 5000 Hz. However, the higher the frequency used, theweaker the overall return signal strength is, assuming the same outputpower per frequency at the Tx.

In another example, the transmitter is able to transmit between 0.1 and100+ watts of power. If two frequencies are transmitted from the singletransmitter, each frequency will have one-quarter of the amount of poweravailable. In this system, power is equal to voltage squared. Therefore,in order to transmit two frequencies out of one band, power issacrificed.

In one embodiment, the radar system (e.g., the CW radar system) isoperable to generate multiple transmission frequencies through one ofthree methods. In one embodiment, the radar system (e.g., the CW radarsystem) transmits two or more frequencies simultaneously from a singleTx antenna. This embodiment reduces the number of Tx/Rx pairs in theoverall system, thus reducing the overall physical complexity of thesystem. A single Tx antenna is operable to transmit a few or even tensof frequencies simultaneously. This approach requires that the powerrequired to transmit multiple frequencies increases as a squaredfunction of each additional frequency. If one frequency is now expandedto two simultaneous frequencies, then the amplifier power required tomatch the single frequency increases from a factor of (1)² = 1 to (2)² =4. In the case where the amplifier is at maximum power setting and anadditional frequency is added, then signal strength is reducedeffectively from a factor of 1/(1)² = 1 to 1/(2)² = ¼. In the case of 3simultaneous frequencies, this transmitted power per frequency falls to1/(3)² = ⅑ of the system’s total output power.

In another embodiment, there are multiple Tx/Rx pairs in the system. Inone embodiment, there is one Tx/Rx pair for each frequency transmitted.This allows the use of multiple amplifiers (one for each Tx antenna) andprovides more overall power transmitted per each frequency. The currentCW radar in FIG. 1D shows two separate Tx/Rx systems in the samestructure. The structure shown is operable to easily handle 3 or moreTx/Rx pairs. The advantage is that output power is operable to bemaximized. A slight loss is discussed above where some power is lost dueto transformer-like losses; typical losses seen amount to no more than3% of the transmitted power. The amount of power lost as discussed aboveis much less than the amount of power lost in the first embodimentwherein multiple frequencies are transmitted from a single Tx/Rx pair.

The third embodiment is a combination of approaches 1 and 2 above toachieve the desired number of frequencies transmitted with the desiredamount of power from the total amplifiers in the system. An additionalissue, whether using approach one, two, or three above is that thetransmission of any two frequencies will also generate a third signalwherein the frequency of the third signal is the beat frequency, or thedifference between the frequencies of the two intended signals. As anexample, transmitting two signals at 300 Hz and 500 Hz from eitherapproach above will also generate a third frequency of 200 Hz (500 Hz -300 Hz). Transmitting three frequencies will produce the threefrequencies and two additional beat frequencies.

In another embodiment, the system includes a plurality of Tx antennas.In one embodiment, the system includes three Tx antennas. Each of theplurality of Tx antennas preferably transmits a different frequencybetween 1 Hz and 1 MHz. The frequencies chosen depend on factorsincluding, but not limited to, the size of the target objects andexpected range between the sensor-head and the target. In oneembodiment, the system operates as a pulsed system (e.g., at higherfrequencies). In one embodiment, the pulsed system uses frequenciesgreater than about 100,000 Hz. However, the pulsed system is notoptimized for total energy on the target.

In a preferred embodiment, each Tx antenna is paired with two Rxantennas. In one embodiment, a first Rx antenna is positioned in frontof the Tx antenna and a second Tx is positioned behind the Tx antenna.Advantageously, this provides improved geolocation accuracy and animproved ability to reject false targets (e.g., in shallow water orwaves). The limit on the number of antennas is governed by the size ofthe sensor-head.

In one embodiment, the plurality of antennas includes between three andten Tx antennas. In another embodiment, the plurality of antennasincludes more than ten Tx antennas. In one embodiment, the fore Rxantenna or the aft Rx antenna are removed. Advantageously, thisembodiment is operable to be used for applications requiring lessconfidence in target geolocation or where environmental noise andclutter are reduced (e.g., in deep water where surface wave returns arenot seen). As most false targets are induced by surface waves, thenumber of false alarms is manageable.

In one embodiment, a single broadband Tx antenna (i.e., more than onedecade in bandwidth) being driven by multiple frequencies (e.g., two tothousands) is operable to replace multiple Tx antennas. Additionally oralternatively, a single broadband Rx antenna is operable to replacemultiple Rx antennas.

In one embodiment, multiple broadband antennas are operable to be usedin the same fashion as multiple narrowband antennas when wide frequencycoverage is desired and/or required. In one embodiment, the systemincludes a three-transmitter broadband antenna system. In oneembodiment, the three-transmitter broadband antenna system covers morethan three decades of bandwidth (e.g., 100 Hz to 100,000 Hz ofinstantaneous bandwidth). Advantageously, broadband antennas areoperable to reduce the overall size of the radar system (e.g., the CWradar system). In another embodiment, the system includes at least twobroadband antennas. In one embodiment, the system includes at least fivebroadband antennas (e.g., nine broadband antennas). Adding additionalantennas increases the cost, the weight, and/or the overall dimensions(e.g., due to separation between antennas) of the radar system (e.g.,the CW radar system). Advantageously, adding broadband antennas allowsfor smaller dimensions of the radar system (e.g., the CW radar system),requiring a smaller vessel and providing for ease of use.

In one embodiment, illustrated in FIG. 66A, the receive antennas areduplicated and separated (e.g., by about 1-2 m) to the side of eachother, creating a second array of receiver antennas. In one embodiment,both sets of antennas are offset from the tow center line by about 0.5 mto about 1 m (about 1.64 ft to about 3.28 ft). In one embodiment, thetransmitter antennas are increased in length to about 1 m to about 2 m(about 3.28 ft to about 6.56 ft) to maintain good electrical isolation.This embodiment improves over other embodiments made up of a singlein-line series of antennas in that this embodiment is operable todetermine whether the target is to the left or right of the sensor headin a single pass within range of the target object. Additionally, thisembodiment produces separate range measurements on the object thatreduces the number of runs over the target necessary to producehigh-quality 3D maps of the sub-surface metal objects. FIG. 66B listsall the labels in FIG. 66A.

In one embodiment, three arrays of receiver antennas are included in thesensor head. In addition to the second array added above, a thirdreceiver antenna array is added along the center line of the sensor headas illustrated in FIG. 67A. The advantage of this embodiment is animprovement in range to target determination and unambiguous direction(e.g., left or right of the sensor track). In one embodiment, thereceiver arrays are positioned between about 0.5 m (1.64 ft) and about 1m (3.28 ft) apart. In one embodiment, the transmitters are increased inlength to about 1 m to about 2 m (3.28 ft to 6.56 ft) to maintain goodelectrical isolation. Advantageously, using three receiver arraysoperates to provide data needed to calculate and display extremely highdetailed 3D maps of the sub-surface distribution of metal objects. Thesystem is operable to create maps with < 0.3 m (1 ft) resolution. FIG.67B lists all the labels in FIG. 67A.

In one embodiment, illustrated in FIG. 68A, the transmitter antennas areoriented vertically, and the receiver antennas are orientedhorizontally. This arrangement has greater clutter return from the oceansurface, but this is only an issue in shallow water surveys of <15 m(49.2 ft). The major advantage of this arrangement is the ability tomaintain good electrical isolation between the Tx and Rx antennas whilekeeping the Tx antennas short. Shorter antennas reduce the overallweight of the sensor head, which is operationally desirable. The systemis operable to provide, in real time or near-real time, the direction ofthe target object relative to the sensor track (e.g., left or right oftrack). This embodiment produces separate range measurements on theobject that reduces the number of runs over the target necessary toproduce high-quality 3D maps of the sub-surface metal objects. In oneembodiment, the sensor head is about 1 m (3.28 ft) to about 2 m (6.56ft) wide, about 4.5 m (14.75 ft) long, and about 0.64 m (2.1 ft) tall.FIG. 68B lists the labels in FIG. 68A.

In one embodiment, illustrated in FIG. 69A, the transmitter antennas areoriented vertically and the receiver antennas are oriented horizontally.This arrangement has greater clutter return from the ocean surface, butthis is only an issue in shallow water surveys of <15 m (49.2 ft). Themajor advantage of this arrangement is the ability to maintain goodelectrical isolation between the Tx and Rx antennas while keeping the Txantennas short. Advantageously, using three receiver arrays operates toprovide data needed to calculate and display extremely high detailed 3Dmaps of the sub-surface distribution of metal objects. The system isoperable to create maps with < 0.3 m (1 ft) resolution. Shorter antennasreduce the overall weight of the sensor head, which is operationallydesirable. In one embodiment, the sensor head is about 1 m (3.28 ft) toabout 2 m (6.56 ft) wide, about 4.5 m (14.75 ft) long, and about 0.64 m(2.1 ft) tall. FIG. 69B lists the labels in FIG. 69A.

In one embodiment, the system includes antennas other than simple dipoleantennas. In one embodiment, the system includes loop antennas (e.g.,cross-polarized loop antennas). In one embodiment, the loop antennas arearranged horizontally and separated along the direction of travel.Advantageously, the loop antennas are operable to expand the sensitivityof the system to magnetic field direction as well as the currentelectric field detection of the dipole antennas. The electronics of thereceiver are operable to block in the direction of the circularpolarization of the transmitter to provide electrical separation. Highergain antennas (e.g., Yagi-Uda) are operable to be implemented in atleast one Tx antenna and/or at least one Rx antenna. Phased arrayantennas are operable to be implemented to improve power at the targetand/or receiver sensitivity. The multi-transmit/multi-receive designdescribed above is an ideal configuration to implement phased arraytechniques.

In another embodiment, polymer antennas with reasonable conductivity(e.g., > 10,000 Siemens/meter (S/m)) are operable to be used for thereceiver antennas. Polymer antennas are operable to be simply formedinto dipole antennas. The lower conductivity, relative to metal, resultsin a slower propagation of the current and voltage along the length ofthe polymer. As a result, the standing wave is operable to form in amuch shorter distance. Antennas suitable for a towed platform areoperable to be formed easily for any conductivity above 10,000 S/m. Forvalues lower than that, other antenna designs are operable to be usedthat are more compact (e.g., see description of electrically shortantennas, infra). An example material is stretch oriented polyacetylenewhich has conductivity values of approximately 80,000 S/m, and a ½ wavedipole antenna is operable to be fabricated with a center frequency of200 Hz that is only 88 mm long. The advantage of polymer antennas is theability to provide greater transmit power when compared to electricallyshort antennas. Some electrically short antennas are less than 1%efficient, while polymer antennas have the potential to reach closer tothe 50% theoretical limit. Polymer antennas also promise the ability forfabrication of a smaller sensor, reducing the overall footprint of thesystem on the towing vessel and the required size of a ROV and/or AUVneeded to tow the sensor.

In another embodiment, polymer antennas are operable to be used for thetransmitter antennas instead of electrical short antennas.

In another embodiment, polymer antennas are used for both the receiveand transmit antennas.

As previously described, in one embodiment, the system includes at leastone electrically short antenna. In one embodiment, the at least oneelectrically short antenna includes a nanomechanical magnetoelectric(ME) antenna, a Goubau antenna, a Foltz antenna, and/or a Rogers coneantenna.

The system is operable to use any antenna configuration that allows forand provides electrical isolation between the Tx and the Rx.

However, electrical isolation is not necessary if the receiver isdesigned such that the receiver is not j ammed by the transmit signal.Methods to prevent the receiver from being jammed by the transmit signalinclude, but are not limited to, logarithmic digitizing circuits,cascade digitizer circuits, dual offset-bias digitizers, and/or high bitdigitizers paired with compression circuits (e.g., multimodallogarithmic, mu law, Voltage Controlled Amplifiers (VCA), opticalcompression, etc.) are compatible with the present invention. Thesemethods make the direct path signal small, while preserving thesensitivity to sense the small constructive or destructive signalsimparted to the receive signal by a target return.

In one embodiment, the radar system (e.g., the CW radar system) includesantennas of a small length and/or a small diameter (e.g., less than 1 m(3.3 ft)). In one embodiment, the antennas have a length and/or adiameter of about 15.2 cm (6 in) to about 30.5 cm (12 in).Advantageously, using antennas of a small length and/or a small diameterallows for a diver to use the radar system (e.g., the CW radar system).FIG. 57 illustrates one embodiment of a handheld radar system 5700. Thehandheld radar system 5700 is operable to be used by a diver 5710. Thehandheld radar system 5700 includes an indicator 5720, a pole 5730, anda radar system 5740. In one embodiment, the indicator 5720 is a visual,audible, and/or tactile mechanism. In one embodiment, the indicator 5720includes a liquid crystal display (LCD). In another embodiment, theindicator 5720 includes at least one light-emitting diode (LED). In oneembodiment, the at least one LED includes at least one red LED, at leastone yellow LED, and/or at least one green LED. In one embodiment, theindicator (e.g., at least one LED, the LCD) is operable to indicate aspecies. In one embodiment, the indicator is operable to indicate adirection of an underwater object. For example, and not limitation, theindicator is operable to indicate a proximity (e.g., nearer, farer)based on movement of the radar system (e.g., by the diver).

The LED indicator illustrated in FIG. 58 consists of a simple two lightsystem and is operable to be mounted on the handle of the sensor. In oneembodiment, a blinking green light indicates the presence of a metalwithin a detection range of the sensor. In one embodiment, a rate atwhich the light blinks indicates a strength of the signal. In oneembodiment, a red LED indicates a normal condition of the system beingoperational but no metallic targets are detected. Alternately, anacoustic indicator, as used in many handheld metal detectors, isoperable to be used, wherein the strength of the tone is directlycorrelated with the strength of the signal. The advantage of thetechnology of the present invention over the current metal detectors onthe market is related to the background noise caused by moving aconventional metal detector through a conducting medium (e.g.,saltwater). The faster the detector head is moved, the louder thebackground signal and the background tone will be. This dramaticallylimits the search rate of a diver using a traditional metal detector.The present invention does not suffer from this background noise,regardless of speed of search.

In one embodiment, the radar system (e.g., the CW radar system) ismounted on an underwater vessel (e.g., a submarine). In one embodiment,illustrated in FIG. 59 , the radar system (e.g., the CW radar system) ismounted on a fin of the underwater vessel. The underwater vessel isoperable to be manned or unmanned. Propellors and/or motors of theunderwater vessel are preferably radio frequency shielded to avoidinterference with the radar system (e.g., the CW radar system).

FIG. 60 illustrates an embodiment of the present invention incorporatingwater jet-based propulsion, which allows the electric motors creatingthe jet to be buried within the hull of the vessel. The only movingexterior part to the vessel hull is the drive jet nozzle.

Alternatively, an even more preferable vessel, illustrated in FIG. 61 ,incorporates multiple ports built into the vessel for different driveand maneuver jets to exit the radio frequency sealed hull of the vessel.

With multiple frequencies being transmitted from a single band radarsystem or a dual band radar system transmitting two distinctfrequencies, the result is that each frequency has its own set ofconstructive and destructive zones that differ in range based on thefrequency (wavelength) of transmission, as illustrated in FIG. 8 . Byusing multiple, simultaneous frequencies, the radar system (e.g., the CWradar system) is operable to provide the exact distance to an objectand/or target. As the distance between the object and/or target and thesensor head of the radar system (e.g., the CW radar system) changes, thesignals received by the Rx antenna or antennae of the radar system(e.g., the CW radar system) transition between constructive anddestructive interference. These transitions depend on the frequency ofthe transmitted signals and are used to measure overall distance betweenthe radar system (e.g., the CW radar system) and an object and/ortarget. The use of multiple frequencies allows for the radar system(e.g., the CW radar system) to detect and identify an object and/ortarget with more detail.

In a pulsed system, distance is calculated in part from the time that ittakes for a sent Tx antenna pulse to reach the Rx antenna afterinteracting with an object and/or target. However, with continuous wavesystems, there is no measure of time because the Tx antenna is alwayssending out a signal. The radar system (e.g., the CW radar system) ofthe present invention solves this distance measurement issue associatedwith current CW radar systems by employing different frequencies withdifferent constructive and destructive zone lengths, as illustrated inFIG. 8 . The combination of received signals of varying frequencies thathave passed through respective constructive and/or destructive zonesafter being reflected off an object and/or target allows the radarsystem (e.g., the CW radar system) to precisely identify each returnsignal, as well as the location of an object and/or target as well asits composition. The radar system (e.g., the CW radar system) also usesthe phase shift and relative signal strengths of the returning signalsto compute distance, metal type, and precise location measurements.

Furthermore, the use of multiple frequencies by the radar system (e.g.,the CW radar system) of the present invention enables the system todetect and/or penetrate steel and iron plate (e.g., relatively thinsteel and iron plate). In the oil and gas industries, a process known as“Pigging” is used to locate a sensor inside a steel pipe. The sensortransmits a frequency low enough to penetrate a steel walled pipe. Theradar system (e.g., the CW radar system) of the present invention isoperable to create these same frequencies by either directlytransmitting a frequency that is low enough to penetrate a steel-walledpipe or by transmitting two separate frequencies, wherein the beatfrequency of the two separate frequencies is low enough to penetrate asteel-walled pipe. For example, if the two frequencies being transmittedfrom a single radar system are approximately 311 Hz and approximately333 Hz, respectively, there is a third signal with a beat frequency alsobeing transmitted at the difference between the two frequencies. In thisexample, this beat frequency is approximately 22 Hz (333 Hz - 311 Hz).This third frequency value, 22 Hz, is the typical frequency used in“Pigging.” It transmits through steel and is operable to be detected bythe dipole antennas of the radar system (e.g., the CW radar system) ofthe present invention.

In one embodiment, the radar system (e.g., the CW radar system) isoperable to perform deep water surveys (i.e., depths > about 305 m (1000ft)). The radar system (e.g., the CW radar system) preferably maintainsthe ability to survey in shallow water (i.e., depths < about 4.6 m (15ft)). The radar system (e.g., the CW radar system) is a multibandcontinuous wave radar system.

Cross Polarization

The radar system (e.g., the CW radar system) of the present inventionuses cross polarization to reduce the direct path energy from Tx to Rxantennas, which deflects any reflected energy from an object and/ortarget. Cross polarization using dipole antennas is accomplished throughphysical orientation. The Tx antenna is oriented 90 degrees from the Rxantenna(s).

FIG. 2 illustrates an antenna setup for Tx and Rx antennas for a radarsystem (e.g., a CW radar system) according to one embodiment of thepresent invention. The Tx antenna is positioned between two Rx antennas.In addition, the Tx antenna is placed at a 90-degree angle in relationto the two Rx antennas.

An added benefit of this embodiment is the noise cancellation providedby the polarization characteristics of the Tx and Rx antennas. Incurrent signals, there are several primary sources of noise. Suddenmovements and/or jerking on any towing device(s) creates significantnoise in the signal received by the Rx antennas, with greater noisecreated in any forward Rx antennas. Another source of noise includesvibration. As the radar system (e.g., the CW radar system) moves throughwater, the turbulence across the structure produces a large amount ofnoise via vibration. Moreover, any flexing of the radar system (e.g.,the CW radar system) during towing and/or collecting causes a Dopplereffect in the signal(s).

FIG. 3A illustrates a cross-polarization orientation for Transmitter(Tx) and Receiver (Rx) antennas according to one embodiment of thepresent invention. The Tx antenna is placed at a 90-degree angle inrelation to all Rx antennas. In one embodiment, the Tx and Rx dipoleantennas are between approximately 20.3 to 76.2 cm (8 to 30 inches) inlength and have diameters between approximately 1.27 to 5.1 cm (0.5 to 2inches). In a continuous radar system such as the present invention, thedirect signal path from the Tx to the Rx antenna(s) is of much highermagnitude than that of the return signal that has interacted with anobject and/or target. Typical radar systems used by the military andcommercial communities use pulsed radar, wherein the Tx antenna sendsout short, pulsed bursts of energy while the Rx antennas are turned offor electrically protected from the direct path energy to avoid theinterference of the direct path energy. The Rx antennas are then turnedon when the Tx antennas are turned off in order to receive only thereturn signal from the object and/or target. However, since thefrequencies of the present invention are extremely low and the resultingwavelengths are long, pulsed radar systems will not work in theconditions where the radar system (e.g., the CW radar system) of thepresent invention is operable to function. Thus, the radar system (e.g.,the CW radar system) uses cross polarization of the Tx and Rx antennasto eliminate the direct path energy from the Tx antenna(s) to the Rxantennas, enabling the system to detect distant targets and/or objectswhile the Rx antennas are located directly next to the bright and loudTx antenna(s).

FIG. 3B illustrates a cross polarization orientation for Tx and Rxantennas according to another embodiment of the present invention. Crosspolarization using dipole antennas is accomplished through physicalorientation. The Tx antenna is oriented approximately 90 degrees fromthe Rx antennas. When using dipole antennas, multiple Tx antennas inclose proximity to one another result in a transformer-like conditionand loss of power will occur if the Tx antennas are too close to oneanother. In a transformer, energy from one Tx antenna will be absorbedby an adjacent Tx antenna such that none of the transmitted energy willpropagate away from the Tx antenna. The result is a direct loss of powerand a need to prevent this lost power from feeding back into the firstTx antenna’s circuitry. In order to minimize these effects, the radarsystem (e.g., the CW radar system) of the present invention ensures afunctional distance has been built into the structure holding theseparate transmitters. This functional distance is a function of howmuch energy loss is acceptable and the specific signal frequencies beingtransmitted by the radar system (e.g., the CW radar system). In oneembodiment, the radar system (e.g., the CW radar system) of the presentinvention separates Tx antennas by approximately 15.2 cm (6 inches) toapproximately 91.44 cm (36 inches). Since the Rx antennas are alsodipole antennas, the angle between the Tx antenna(s) and the Rx antennasis approximately 90 degrees, maximizing the benefits ofcross-polarization.

FIG. 3C illustrates a cross polarization orientation for Tx and Rxantennas according to another embodiment of the present invention.

FIG. 4 illustrates an antenna setup for Tx and Rx antennas for a radarsystem (e.g., a CW radar system) according to one embodiment of thepresent invention. The Tx antenna is positioned between two Rx antennas.The Tx antenna is placed at a 90-degree angle in relation to the two Rxantennas.

In addition, a third source of noise is the electronic equipmentpowering, controlling, connected to, and/or in close proximity to theradar system (e.g., the CW radar system). All electronics have noiseassociated with them and must be accounted for and/or corrected for. Thelargest source of drift seen in the system is thermal drift in theanalog amplifiers. Without correction, drift values of over 3 dB havebeen observed during the duration of a survey. Strict temperaturecontrol of the amplifier boards and low thermal drift components reducethis effect until it is manageable in the collection phase and removablein the processing and analysis phase using a variety of statisticalanalysis techniques.

In one embodiment, a single Tx antenna is coupled with at least one Rxantenna (e.g., 1 Rx antenna, 2 Rx antennas). In a preferred embodiment,the single Tx antenna is mutually orthogonal with the at least one Rxantenna, making the system fully 3-dimensional (i.e., 3 axes).

In one embodiment, a pinpoint localization system (PLS) is placed (e.g.,by a diver, by an AUV) on a pre-surveyed grid, which is based ondetection and localization performed by the radar system (e.g., the CWradar system). The PLS is swept in power and frequency over a period oftime (e.g., after the diver leaves). The PLS is moved to the next pointin the grid and the process is repeated until all grid points aresurveyed. Analysis of the strength of the target response to power andfrequency is then used to localize the object relative to the grid inthree dimensions and the difference in frequency response is used totype the material of the target (e.g., species identification).

FIG. 50 illustrates one embodiment of a PLS with 2-axes. The PLSincludes a horizontal Tx antenna and a vertical Rx antenna.Alternatively, the PLS includes a vertical Tx antenna and a horizontalRx antenna when the survey field is nominally >20 m (65.6 ft) below thesurface of the ocean.

FIG. 51 illustrates one embodiment of a PLS with three axes. The PLSincludes a Tx antenna (e.g., horizontal Tx antenna), a horizontal Rxantenna, and a vertical Rx antenna. In one embodiment, the Tx antenna isa vertical Tx antenna. There is a balance between the lowest frequencyused, the depth of the ocean floor below the ocean surface, the powerlevel of the transmitter, and how long a sample is taken (e.g., longersampling allows time averaging to remove wave effects).

FIG. 62 illustrates one embodiment of a PLS with three axes. The PLSincludes a vertical Tx antenna with four Rx antennas in a square aroundthe Tx antenna. Unlike the prior embodiments, this embodiment allows foran area search of over 20 m (65.6 ft) in all directions (latitude,longitude, and depth). The system geolocates relative to the Tx antennato < 1 m in all three dimensions.

FIG. 63 illustrates one embodiment of a PLS with three axes support andis fully target orientation independent. This embodiment allows for anarea search of over 20 m (65.6 ft) in all directions (latitude,longitude, and depth). The system geolocates relative to the Tx antennato < 1 m in all three dimensions.

In one embodiment, the system includes a sequential transmit and receiveas shown in FIG. 52 . A first transmit and receive site transmits to asecond transmit and receive site. The second transmit and receive sitetransmits to a third transmit and receive site, and so forth.

In one embodiment, the PLS frequencies are between 1 Hz to 1 MHz. In apreferred embodiment, the PLS frequencies are in the 1,000 Hz to 40,000Hz range. The transmitted waveforms are operable to be continuous wave,swept, or pulsed. However, pulsed waveforms typically provide too low ofan average power to positively localize an object in the normal surveytime frame. Continuous wave provides the highest average power perfrequency transmitted.

FIG. 53 illustrates one example of a continuous wave search signal for aPLS.

Frequency, power, and receiver sensitivity must be maintained withprecision over length of the collection across the grid to allow foreach survey point to be merged. This is a significant driver for thedesign of the receiver system as long-term stability in analog circuitsmay be difficult if not corrected. In one embodiment, grids are operableto have about 5 m to about 25 m in survey points. Other distances arecompatible with the present invention.

In one embodiment, multiple PLS units are operable to be placedsimultaneously. As attenuation between grid points is significant, evenat 5 m, electrical isolation is maintained. Using about 9 to 25 or moreunits (e.g., with 5 m grids), it is possible to have a singletransmitter acting as the source for all PLS units. FIG. 54 illustratesone embodiment with a single Tx antenna with multiple Rx antennas.

In another embodiment, the Tx antennas at various locations within thegrid (array) are operable to be active (e.g., on the corner of thearray) and the receivers are all operable to be active. Changing therelative phase of the Tx antennas changes the focus of the energy in thesub-bottom, allowing scanning with high precisions. Grid spacing isoperable to be optimized for the location of the Tx antennas and the Rxantennas. FIG. 55 illustrates one embodiment with multiple Tx antennasand multiple Rx antennas.

In yet another embodiment, all PLS units are operable to be active. Inone embodiment, relative phase changes focus the antenna with thepotential for power on the target. FIG. 56 illustrates one embodiment ofmultiple Tx antennas and multiple Rx antennas with phasing for focus anarea of survey.

In still another embodiment, multiple PLS units are operable to bepositioned where all PLS units transmit, but each PLS unit has anassigned frequency offset. Advantageously, this embodiment allows foridentification of the Tx antenna and its location relative to everyother unit. In one embodiment, offsets (e.g., ≥ 1 Hz) are operable toprovide sufficient separation to identify each Tx antenna. A significantadvantage of multiple PLS systems operating simultaneously (e.g., eitherone Tx antenna or multiple Tx antennas operating simultaneously) is thesignificant reduction in the stability requirements on the Rx antennas.Because the entire field is surveyed simultaneously, the length ofsurvey drops from hours to minutes dramatically reducing the drift perunit time requirements on the receiver analog circuitry.

Drift current, or electronics drift, is caused by electric force, i.e.,charged particles get pushed by an electric field. Electrons, beingnegatively charged, get pushed in the opposite direction of the electricfield, but the resulting conventional current points in the samedirection as the electric field. The radar system (e.g., the CW radarsystem) of the present invention must account for drift current fromelements including, but not limited to, temperature, vibrations, and/orsystem electronics. These elements have a natural drift state. Ifunaccounted for, excess noise is created within the system andelectronic saturation from the noise will effectively overpower thetarget signal strength. Therefore, it is important for the radar system(e.g., the CW radar system) to maintain a balanced signal-to-noiseratio. The CW radar uses multiple elements to reduce or controlelectronic drift. The first is through DC (Direct Current) biasingcontrol. The second is through Analog Filtering. The third is throughclimate control of the electronic boards/elements during operations. Theelectronic components are mounted in thermal electric coolers/heaters tomaintain constant temperatures during operations. Environmentaltemperature fluctuations are maintained to less than approximately 1° C.(C) through a combination of heating and cooling. In one embodiment, theradar system (e.g., the CW radar system) is operated at a temperaturerange of approximately 4° C. to 22° C. to avoid thermal drift.

Additionally, several sources of signal clutter must be accounted for.These include, but are not limited to, the reflection of the transmittedsignal off the surface of the water above the radar system (e.g., the CWradar system) and the reflection of the transmitted signal off thebottom of the ocean. Regarding the reflection off the surface of thewater, if the surface was perfectly flat, energy from the Tx antenna(s)would be completely absorbed at the surface. However, the surface isalmost never perfectly flat due to wave action, ocean swells, wakescaused by other objects, winds, currents, etc., which result indisturbances that create a reflection at the air-water boundary,bouncing energy towards the Rx antenna(s). This is operable to amount toapproximately 0.00001 to as much as approximately 0.01 Watt of variancein signal from the surface reflection. In one embodiment, the signalreflection off the surface of the water is most noticeable when theradar system (e.g., the CW radar system) is within 15.2 m (50 ft) of thesurface of the water.

The reflection off the bottom of the ocean is a second source ofclutter, but much less so than the reflection off the surface of theocean. Because sand is typically a mixture of water and rock, theboundary layer effects are minimal. In the case of reef environments, orother rock formations, the boundary layer effects are also minimal, butare also operable to create noise components that need to be accountedfor during post-processing.

In another embodiment of the invention, as illustrated in FIG. 70A, atleast one transmitter and at least one receiver are located in a fixedposition on the ocean floor. The Tx and Rx antennas are cross-polarizedif collocated as a means of reducing direct-path saturation of thereceiver, or the antennas are otherwise electrically isolated byseparation and/or cross-polarization. The radar system (e.g., the CWradar system) continuously emits at least one frequency when a movingmetal object enters the detection range of the system. The Rx antennaand receiver system detects the change in signal level, eitherconstructive or destructive, and reports the detection to a vessel inthe area via fiber-optic or wire. FIG. 70B lists all the labels in FIG.70A.

In another embodiment, multiple Tx and Rx antennas are operable to bedeployed in an area to act as a detection fence-line. One embodiment isillustrated in FIG. 71A where multiple Tx/Rx nodes are linked viafiber-optic or wire. Each node is operable to act independently using adifferent set of frequencies or they are operable to act in concertusing the same frequency and/or frequencies. The nodes process thereturns on-board and relay detection information to a hub forrebroadcast to a surface vessel. This is operable to be either by RFcommunications which are highly covert or by fiber-optic or wiredtether. Making use of detections from multiple nodes allows thedetermination of the position and direction of motion of the surfaceand/or sub-surface targets. FIG. 71B lists all the labels in FIG. 71A.

In another embodiment, illustrated in FIG. 72A, multiple systems areinterconnected via RF communication. The systems are deployed in such away to identify the location and direction of travel of surface andsub-surface vessels (manned or unmanned) and/or divers. The nodes areoperable to work at the same frequency or set of frequencies ordifferent frequency or frequencies. Detection information is relayedfrom each node, possibly being relayed through a number of intermediarynodes until the information reach the hub node which relays theinformation to a land-based control system. FIG. 72B lists all thelabels in FIG. 72A.

In another embodiment, illustrated in FIG. 73A, multiple nodes (e.g., Txonly, Rx only, Tx/Rx combined) are deployed in a pattern to surveil aspecific region. The nodes perform autonomous on-board detection andrelay detection information (e.g., signal strength, frequency, time ofdetection, raw data from the detection window, etc.) via RFcommunication links which are inherently covert and secure. Detectioninformation is eventually relayed to a hub node which is operable torebroadcast the information to a surface vessel. FIG. 73B lists all thelabels in FIG. 73A.

In another embodiment, the nodes are replaced with nodes similar tothose shown in FIG. 62 and FIG. 63 . These nodes provide direction aswell as range information.

Phase Shift

When using multiple Rx antennas of differing electrical path lengths inconjunction with continuous wave (CW) transmissions, a phase shiftoccurs in the signals between each Rx antenna. If the path lengths fromthe Tx transmitter antenna to the target and then to the Rx antennas forthe multiple Rx antennas were identical, there would be no phasedifference between the signals received by each antenna. This phaseshift occurs only under a very precise set of conditions, including whenmultiple Rx antennas are placed perpendicular (90 degrees) or nearperpendicular to the direction the system is being towed. In oneembodiment, one transmitter has four receivers, two forward and two aft,with each spaced between approximately 1-3 meters away from the Tx. Inanother embodiment, one transmitter has two receivers, one forward andone aft, with each spaced between approximately 1-3 meters apart.

FIG. 5 illustrates an antenna setup for Tx and Rx antennas with anindication of the return length differences between Rx antennas for aradar system (e.g., a CW radar system) according to one embodiment ofthe present invention. The Tx antenna sends out a signal in search ofobjects in a saltwater environment. Once detected, the signal is firstreceived by the forward Rx antenna, traversing a first return pathlength (Rx₁). As the radar system (e.g., the CW radar system) passesover the detected object, the signal is received by the aft Rx antenna,traversing a second return path length (Rx₂). Because the system is a CWtransmission and the return path lengths of the two Rx antennas aredifferent, there is a phase difference between the signals received bythe respective Rx antennas. The phase shift is used to distinguish anobject and/or target from background noise and approximate the distancebetween the at least one Tx antenna and the at least one Rx antenna andthe object(s) and/or target(s).

In one embodiment, the radar system (e.g., the CW radar system)’sconfiguration enables the use of two separate transmitters. In order toaccommodate this, the frequency range between the two transmitters needsto be large enough so that the cutoff frequencies block the twotransmitters from saturating the other’s receivers. Because the twotransmitters are perpendicular, the receivers from one transmitter areparallel to the other transmitter and only the frequency cutoff of theantennas will block the opposing transmitter’s signal.

FIG. 6 illustrates a phase shift between Rx antennas for a radar system(e.g., a CW radar system) according to one embodiment of the presentinvention. The radar system (e.g., the CW radar system) of the presentinvention looks for the blue channel (Rx₁) to lead to the red channel(Rx₂) in either an increase in signal strength (constructive) or adecrease in signal strength (destructive) as the system gets closer toan object and/or target. However, it is possible for some signals tosimultaneously experience constructive interference on one Rx antennaand destructive interference on the other Rx antenna. When detectingmultiple targets at various ranges, it is possible for some signals tobe constructive and others to be destructive due to distance andorientation from the system. In order to compare the blue channel (Rx₁)to the red channel (Rx₂), the radar system (e.g., the CW radar system)normalizes the signals using data recorded in the previous few minutesand subtracts this signal data from the current signal. The previous fewminutes of data serves as a baseline for the radar system (e.g., the CWradar system). As more data is collected, the baseline is adjusted. Thisdynamic baseline adjustment accounts for all sources of signal noise andvariation and ensures that all signals from the radar system (e.g., theCW radar system) are normalized, improving system accuracy andefficiency. If no targets were present, both channels would indicatesignal readings of zero after normalization. Due to fluctuations inelectronics and other equipment, the radar system (e.g., the CW radarsystem) is operable to detect approximately -70 to approximately -179decibel watts (dBW) of signal from the combined noise inputs. Thisequates to an overall detection sensitivity of approximately1/1x10^(17.9) Watt of signal, or it represents a minimum detectablesignal of 1.032 nV in voltage. In one embodiment, the signal received bythe radar system (e.g., the CW radar system) in the presence of anobject and/or target is at least 45 dB above the combined noise floorafter post processing.

The phase (φ) difference between the multiple Rx antennas is a compositerelationship between the direct path signal, the condition of the oceansurface, the vibration in the system’s structure, variations occuring atthe tow line, and the object and/or target being detected. The magnitudeof the signal is proportional to the phase difference between the twosignals such that a larger phase difference results in a strongersignal. Therefore, in effect the phase and magnitude of the timedifference signal are the same measurement, where one is easier toidentify at various times. In one embodiment, the system uses the changein phase signal to detect an object and/or target. In anotherembodiment, the system uses the change in signal strength to detect anobject and/or target.

The wavelength in the Rx antenna(s) is equal to the wavelength in the Txantenna, only with a phase shift based on the distance from the Txantenna, the obj ect/target, and the Rx antenna(s). In one embodiment ofthe present invention, when this distance is between approximately 31meters (m) and approximately 119.4 m, the signals create a destructiveinterference, decreasing the total signal strength below the directpath.

The wavelength (c(f)/frequency, where c(f) represents the speed ofpropagation of the electromagnetic wave which also changes as a functionof frequency, temperature, and/or salinity when in saltwater) in the Rxantennas is equal to wavelength in the Tx antenna(s), but the signalsare phase-shifted based on the distance from the Tx antenna(s) to theobject and/or target and back to the Rx antennas. Thus, the phase shiftis associated with the difference in distance that the two Rx antennasare perceiving.

For example, if the CW radar system is transmitting at approximately 283Hz, the perceived wavelength is equivalent to approximately 59.7 massuming water salinity of approximately 4.95 Siemens, as opposed toapproximately 1,000,000 m if transmitted in open air. The path length isa measurement from Tx antenna-to-object/target-to-Rx antennas. In thisembodiment, the path length is equal to two-thirds of the wavelength, orapproximately 38.6 m, and produces constructive interference in anysignal returning from the object/target to the Rx antennas. The resultis a direct signal strength of approximately 3.5 dBW from the Tx antennato either Rx antenna, after amplification from the CW radar system ofthe present invention. The return signal from an object and/or targetthat is less than approximately 10 m away will cause the signal in theRx antennas to increase by more than approximately 1 dBW due toconstructive interference. Destructive interference will have theopposite effect and cause the signal to be lower in signal strength.

In another example, if the radar system (e.g., the CW radar system) istransmitting at approximately 180 Hz, the perceived wavelength isequivalent to approximately 74.8 m assuming water salinity ofapproximately 4.96 Siemens, as opposed to approximately 1,670,000 m iftransmitted in open air. The path length is a measurement from Txantenna-to-object/target-to-Rx antennas. In this embodiment, the pathlength is equal to two-thirds of the wavelength, or approximately 49.9m, and produces constructive interference in any signal returning fromthe object/target to the Rx antennas. The result is a direct signalstrength of approximately 3.5 dBW from the Tx antenna to either Rxantenna, after amplification from the radar system (e.g., the CW radarsystem) of the present invention. The return signal from an objectand/or target that is less than approximately 10 m away will cause thesignal in the Rx antennas to increase by more than approximately 0.1 to0.5 dBW due to constructive interference. Destructive interference willhave the opposite effect and cause the signal to be lower in signalstrength.

The radar system (e.g., the CW radar system) of the present inventiondetects a plurality of phase shift samples from a plurality of samples.In one embodiment, the radar system (e.g., the CW radar system) isoperable to detect between approximately 500 to 2000 samples of phaseshift for every 250,000 samples recorded depending on the transmittedfrequency. Additionally, multiple effects are detected in the currentsystem in addition to phase shift between antennas. These include, butare not limited to, differences in signal strength between the Rxantennas and variations in frequency of the signals at each Rx antenna.Although the Tx antenna is producing a constant tone/frequency, thereare Doppler effects that occur due to vibrations in the physicalstructure of the system that result in signal differences between eachRx antenna.

FIG. 7A illustrates variances in signal strength between Rx₁ and Rx₂antennas for the Rx₁ antenna according to one embodiment of the presentinvention.

FIG. 7B illustrates variances in signal strength between Rx₁ and Rx₂antennas for the Rx₂ antenna according to one embodiment of the presentinvention.

FIG. 7C illustrates variances in frequency using a lower frequencyaccording to on embodiment of the present invention.

FIG. 7D illustrates variances in frequency using a Tx frequencyaccording to one embodiment of the present invention.

FIG. 7E illustrates variances in frequency when using a higher frequencyaccording to one embodiment of the present invention.

Location and Classification

In one embodiment, the radar system (e.g., the CW radar system) of thepresent invention is active sensor-based using electrical conductivity.With an active sensor, signal strength, frequency, and direction areoperable to be increased and/or controlled based on the Tx’s inputs,polarization, and physical characteristics. An active sensor systemincreases its operating range by controlling both Tx and Rxcharacteristics. Ferrous material, including, but not limited to, ironand steel, and non-ferrous material, including, but not limited to,gold, silver, copper, and/or aluminum, are actively excited by the Txand the EM waves. This creates an electrical current due to thematerial’s conductivity. The physical shape of an object and/or targetwill produce a return EM wave that is detected by the radar system(e.g., the CW radar system)’s Rx antennas. The characteristics of thereturn EM wave are a result of the relationship between the Tx antennasand signals, the Rx antennas and signals, and all conductive materialcomposing and surrounding the total system. Material, such as sand,soil, and/or rock, has such low conductivity that they appeartransparent to the Rx antennas, while all conductive materials willproduce some level of detection in the Rx antennas.

TABLE 1 Conductivity of Non-Ferrous & Ferrous Metals MaterialConductivity (S/m) Sliver 6.3E+07 Copper (annealed) 5.80E+07 Gold4.11E+07 Aluminum 3.77E+07 Brass (66% Cu, 34%Zn) Copper (annealed)Carbon 2.56E+07 Tungsten 1.79E+07 Zinc 1.67E+07 Cobalt 1.60E+07 Nickel1.43E+07 Iron 1.03E+07 Platinum 9.52E+06 Tin 9.17E+06 Lead 4.57E+06Titanium 2.38E+06 Stainless Steel 1.45E+06 Mercury (liquid) 1.04E+06Bismuth 8.70E+05 Carbon 2.00E+05 Distilled Water 1.00E-04 Dry sandy soil1.00E-03 Fresh water 1.00E-02 PET 1.00E-21

In one embodiment, the radar system (e.g., the CW radar system)transmits a signal from the Tx antenna(s) by creating a specificfrequency through the use of a signal generator. In one embodiment, thesignal generator functionality includes, but is not limited to, dualchannel output, a sampling rate of approximately 1.5 Mega Samples persecond (MSa/s), generation of lower-jitter Pulse waveforms, support foranalog and digital modulation types, sweep and burst functions, aharmonics generator function, a high precision frequency counter,standard interface compatibility (e.g., universal serial bus (USB) Host,USB device, local area network (LAN), etc.), a display, channelduplication functionality, and/or remote control operability. In oneembodiment, the radar system (e.g., the CW radar system) uses a SIGLENTSDG-1025 signal generator. In one embodiment, the radar system (e.g.,the CW radar system) uses a RIGOL DG-1022 signal generator. In anotherembodiment, the radar system (e.g., the CW radar system) uses a SIGLENTSDG-1032X signal generator. In another embodiment, the radar system(e.g., the CW radar system) uses a waveform signal generator. In anotherembodiment, the radar system (e.g., CW radar system) uses a PC computercontrolled Digital-to-Analog Converter on a PCIe bus mounted cardcapable of generating two or more simultaneous signals which areoperable to be simple tones (e.g., differential or single-ended) orcomplex time-frequency dependent waveforms. The normal operatingcondition is to generate a single tone per board output as thismaximizes transmitted power.

In one embodiment, the radar system (e.g., the CW radar system)transmits a signal from the Tx antenna(s) by using a transmittercomputer to create a digital, differential sinewave signal, which isoperable to be sent to a digitizer board. A low voltage (+/- 1 V)sinewave is produced and is then used as an input into a sound stereoamplifier. In one embodiment, the sound power amplifier is operable toamplify the low voltage signal, thereby producing an output signal withpower between approximately 3500 watts (W) and approximately 5000 W, andis further operable to produce an output signal with amplitude betweenapproximately +/- 20 V and approximately +/- 600 V. The voltage (poweroutput) limitations of the Tx signals is restricted by the properties ofthe wires within the Tx antennas. In one embodiment, the Tx antenna useslarger gauge wires and is operable to produce voltages in excess of 600V. In another embodiment, the Tx antenna produces signals betweenapproximately 5-20 V.

In one embodiment, the output from the transmitter computer is adifferential output (i.e., two signals) that are 180 degrees out ofphase from one another. Together, these two signals make up a sinusoidalwave. The computer outputs are sent to the power amplifier where thecomputer outputs are amplified in a balanced fashion such that theoutputs from the power amplifier channels are still equal magnitude andopposite phase.

In another embodiment, the computer generates single-ended low-voltagesinewaves (tones). The tones are different for each output channel. Thelow-voltage signals are sent to a multi-channel power amplifier whichamplifies the signal that is then transmitted to the vicinity of thetransmit antennas using coaxial cables. Near the transmitter antenna,the single-ended, unbalanced signal is converted into a balanced signalusing a BALUN which then drives the antenna.

The returning signal from the Rx antenna(s) is also a differentialsignal. The return signal is sent from the radar system’s (e.g., the CWradar system’s) sensor head up through a data cable to a dinghy. Thedinghy contains a global positioning system (GPS) that sends a GPSposition through the data cable, along with all the differential signalsfrom each Rx antenna, back to a towing vessel. The incoming signals tothe towing vessel are received by at least one impedance matching boardthat matches the Rx antenna impedance to that of the amplifier boards,which then pass the signal to the receiving computer’s digitizer boardafter amplification. In one embodiment, the impedance is fine-tuned forthe radar system (e.g., the CW radar system) setup instead of having aset resistor value. In one embodiment, the impedance matching does notdrift and does not need to be readjusted once it is matched. Theincoming analog signal from the Rx antenna(s) is digitized in order tobe used by the radar system (e.g., the CW radar system)’s source code.In one embodiment, the GPS device used on the dinghy and the towingvessel are differential GPS devices.

FIG. 8 illustrates object detection ranges for a radar system (e.g., aCW radar system) according to one embodiment of the present invention.The dot at the center represents the radar system (e.g., the CW radarsystem). A combination of constructive and/or destructive alternatingbands indicate which zone the object/target is located in based on theobject/target’s distance from the Tx/Rx antenna system. In oneembodiment, the signal received by the outer channel (Rx₁ channel) isused to analyze the signal received by the inner channel (Rx₂ channel)to determine an upward rise in signal strength (constructive) and/or adownward drop in signal strength (destructive) as the radar system(e.g., the CW radar system) is towed/pulled over the object/target. Inorder to compare the Rx₁ and Rx₂ channels, the signals are normalizedusing a previously selected time interval of data collected in theabsence of an object/target, which is then subtracted from the currentsignal data. If no objects/targets were located or present, bothchannels would equate to zero.

In one embodiment, the radar system (e.g., the CW radar system) of thepresent invention uses three principal time domain signals in order tolocate objects/targets: signals in the forward Rx antenna, signals inthe aft Rx antenna, and the signal difference between the forward andaft Rx antennas. These three signals are then analyzed with respect toenergy, power, standard deviation, and phase. All signals are comingfrom the variation of signals in the time domain.

By using multiple frequencies, the radar system (e.g., the CW radarsystem) of the present invention is able to not only detect and locateobjects and/or targets, but classify them as well. This is performedusing the relative signal strength and phase between signals ofdifferent frequencies, enabling the radar system (e.g., the CW radarsystem) to distinguish between materials including, but not limited to,all ferrous and non-ferrous metals (e.g., gold and/or silver objects).Signals of any frequency are operable to be used to detect all metalobjects, but the spectral response or relationship between thefrequencies determines the type of metal the object is made of. If anobject(s) is made from multiple metal types, the return signal of theradar system (e.g., the CW radar system) is a pattern that indicates theindividual metals associated with an object and/or target. Becausedifferent metals have different conductivities, they will reflect eachfrequency differently. The signal response from an object and/or targetalso depends on if the object and/or target is located in a constructiveor destructive interference zone. The location and width of theconstructive and destructive zone is different for each frequency.Therefore, the radar system (e.g., the CW radar system) is operable todetect and classify objects and/or targets using the spectroscopyresponse of objects and/or targets using multiple frequencies.

In another embodiment, using three frequencies, the radar system (e.g.,the CW radar system) uses the center frequency to baseline the signalresponse of the target object. This embodiment effectively removes theimpact of the size of the object on the return strength. The change inthe signal strength between the center frequency and the upper and lowerfrequencies when taken independently and then compared indicate theconductivity of the material causing the return signal.

In another embodiment, using 3D imaging (discussed infra), the radarsystem (e.g., the CW radar system), first determines a precise locationof the object in three dimensions either in an absolute or a relativecoordinate system. Next, the return of each survey line is adjusted forthe range affects (e.g., frequency dependent attenuation) between theradar system and the object and also for the size effects on the return(e.g., Rayleigh region radar cross section correction of the return).

FIG. 9 illustrates a precision detector for a radar system (e.g., a CWradar system) according to one embodiment of the present invention. Theradar system (e.g., the CW radar system) is capable of using a single Txantenna and a single Rx antenna to precisely locate objects and/ortargets. The single Tx antenna and the single Rx antenna are connectedto one another via a non-conducting pipe/rigid structure. When the radarsystem (e.g., the CW radar system) is stationary, this antenna setup isoperable to locate and detect objects and/or targets. In a stationarystate, power and frequency will vary across the radar system (e.g., theCW radar system) while data is being collected. Moreover, by using asingle Tx antenna and a single Rx antenna when the radar system (e.g.,the CW radar system) is stationary, the radar system (e.g., the CW radarsystem) is operable to pinpoint an object and/or target and determinethe object’s and/or target’s precise depth. In one embodiment, thesingle Tx antenna and single Rx antenna are the same antennas alreadyincorporated within the radar system (e.g., the CW radar system). Inanother embodiment, the single Tx and single Rx antenna setup is aseparate, detachable antenna setup from the main body of the radarsystem (e.g., the CW radar system).

The constructive and destructive zones for the radar system (e.g., theCW radar system) of the present invention are determined using thedistance from the radar system (e.g., the CW radar system) to anobject/and or target and the return path of the Tx signal to the Rxantennas. This distance represents the total distance associated with asignal from its transmission from the Tx antenna, to its reception bythe Rx antenna(s). This distance accounts for frequencies in use by theradar system (e.g., the CW radar system) as well.

FIG. 8 illustrates a graph indicating constructive and destructivesignals associated with locating an object in a saltwater environmentaccording to one embodiment of the present invention. When an objectand/or target is detected by the radar system (e.g., the CW radarsystem) in a constructive zone, an increase in signal strength isdetected as the radar system (e.g., the CW radar system) approaches theobject and/or target, and a decrease in signal strength is detected asthe radar system (e.g., the CW radar system) moves away from the objectand/or target. When an object and/or target is detected by the radarsystem (e.g., the CW radar system) in a destructive zone, a decrease insignal strength is detected as the radar system (e.g., the CW radarsystem) approaches the object and/or target, and an increase in signalstrength is detected as the radar system (e.g., the CW radar system)moves away from the object and/or target. In one embodiment, thisappears on a graph as a double-hump shape, indicating that all Rxantennas detected the object and/or target.

FIG. 11A illustrates a graph indicating constructive and destructivezones over time created by the signals collected using the sensor head,a tow vessel, and a dinghy associated with locating an object in asaltwater environment according to one embodiment of the presentinvention. The movement of the sensor head associated with a towing bythe vessel system determines when and where signals are transmitted andreceived by the corresponding Tx and Rx antennas. The radar system(e.g., the CW radar system) must monitor its output power product andthe change in received power at the fore and aft receiver antennas todetermine whether the power product result is constructive, destructive,or clutter.

FIG. 11B illustrates a graph indicating the energy product for a radarsystem (e.g., a CW radar system) according to one embodiment of thepresent invention.

FIG. 11C illustrates a graph indicating antenna signal strengthassociated with constructive and destructive zones of a radar system(e.g., a CW radar system) according to one embodiment of the presentinvention.

In one embodiment, a towing vessel attaches a tow line and/or tow cableto a dinghy, wherein the dinghy is attached, via a second tow lineand/or tow cable, to the sensor head of the radar system (e.g., the CWradar system) of the present invention. In one embodiment, the radarsystem (e.g., the CW radar system) includes a tow line and/or tow cablefor connecting the towing vessel to the dinghy and a tow line and/or towcable for connecting the dinghy to the radar system (e.g., the CW radarsystem) as well as a data tow line and/or data tow cable connecting thetowing vessel to the dinghy and a data tow line and/or data tow cableconnecting the dinghy to the radar system (e.g., the CW radar system).In one embodiment, the dinghy includes a global positioning system (GPS)receiver. Because the radar system (e.g., the CW radar system) islocated underwater, the GPS receiver must be placed on the attacheddinghy and not the radar system (e.g., the CW radar system). An initialcalibration of the radar system (e.g., the CW radar system) componentsis performed and a baseline for object and/or target geolocation data isestablished. In one embodiment, the baseline signal for a constructivezone is louder and the signal is elevated. In one embodiment, thenegative energy in a destructive zone is quieter. The towing vesseltravels in a line over a target survey area at an optimum speed. Theradar system (e.g., the CW radar system) is operable at speeds betweenapproximately 0 to >30 kts. In one embodiment, the optimum speed of thetowing vessel is between approximately 3 kts to 8 kts to reducevibrational noise interference. Once the towing vessel, the dinghy, andthe radar system (e.g., the CW radar system) have traveled over thetarget survey area, the towing vessel turns approximately 90° andspecifies a new line of travel over the target survey area. In oneembodiment, the towing vessel turns clockwise. In another embodiment,the towing vessel turns counterclockwise. This new line is covered bythe towing vessel, the dinghy, and the radar system (e.g., the CW radarsystem). In one embodiment, the radar system (e.g., the CW radar system)is operable to send and receive signals within a range of approximately30-100 m from each side of the radar system (e.g., the CW radar system)when traveling in a line, resulting in a total swath width ofapproximately 60-200 m in one pass. In another embodiment, the radarsystem (e.g., the CW radar system) is operable to send and receivesignals within a range of 200 m from either side of the radar system(e.g., the CW radar system) when traveling in a line, resulting in atotal swath width of 400 m per pass. In one embodiment, the lines oftravel taken by the towing vessel, the dinghy, and the radar system(e.g., the CW radar system) over the target survey area areapproximately 100 m apart from each other.

In one embodiment, the towing vessel, the dinghy, and the radar system(e.g., the CW radar system) traverse the same part of the target surveyarea multiple times in order to more accurately identify the size,structure, shape, and composition of the object and/or target. Thisprocess is repeated in a set pattern until the target survey area hasbeen completely mapped by the towing vessel, the dinghy, and/or theradar system (e.g., the CW radar system). By travelling over the targetsurvey area in a designated pattern using the towing vessel, the dinghy,and the radar system (e.g., the CW radar system), the radar system(e.g., the CW radar system) collects data that are operable to beassociated with the geolocation of underwater ferrous and/or non-ferrousobjects. This is because when the radar system (e.g., the CW radarsystem) travels over an object and/or target, a change in signalstrength is detected followed by a change in signal strength in theopposite direction as the towing vessel, the dinghy, and the radarsystem (e.g., the CW radar system) moves away from a detected objectand/or target. When the data has been processed, the radar system (e.g.,the CW radar system) returns Gaussian-like curves in the area where anobject and/or target has been located, indicating detection from thefront and rear antennas of the radar system (e.g., the CW radar system).In one embodiment, the radar system (e.g., the CW radar system) returnslines and/or scatter trails indicating an object and/or target. Theradar system (e.g., the CW radar system) passes over an area multipletimes in order to generate tighter lines around the object and/ortarget. In one embodiment, the radar system (e.g., the CW radar system)is connected directly to the towing vessel via a single tow line,without the use of a connecting dinghy.

In one embodiment, the radar system (e.g., the CW radar system) detectschanges in signal strength the first time it passes over an objectand/or target. The radar system (e.g., the CW radar system) then passesover the same area again and varies the power level of the signal inorder to collect more data on the object and/or target. A lower powersignal provides more detail and higher fidelity images of the objectand/or target. In one embodiment, the power level of the signal dependson the pattern used to survey the area. In one embodiment, the radarsystem (e.g., the CW radar system) makes tighter passes over the samepart of the target survey area in order to detect more information aboutan object and/or target in that part of the target survey area. In oneembodiment, the pattern that the radar system (e.g., the CW radarsystem) takes over the target area and the power variations in thesignal are set before the radar system (e.g., the CW radar system)begins traversing the target area in order to capture full detail of thetarget area. In another embodiment, the pattern that the radar system(e.g., the CW radar system) takes over the target area and the powervariations in the signal are dependent on the readings of the Rxantenna. When the radar system (e.g., the CW radar system) detectschanges in signal strength the first time it passes over an objectand/or target, it modifies the subsequent path and signal transmissionin order to obtain further information about the detected object and/ortarget. In one embodiment, the power level of the signal used toidentify the object and/or target is controlled by the gain of the Rxamplifier board. In another embodiment, the power level of the signalused to identify the object and/or target is controlled by the Txantennas. In yet another embodiment, the power level of the signal usedto identify the object and/or target is controlled by both the Tx andthe Rx antennas. In one embodiment, the radar system (e.g., the CW radarsystem) is operable to identify the size, structure, and shape of anobject and/or target with multiple radar readings. For example, theradar system (e.g., the CW radar system) is operable to identify ribs ona barge and brass shells in an underwater environment.

In one embodiment, the radar system (e.g., the CW radar system) includesat least two Tx antennas, at least two Rx antennas forward of the Txantennas, and at least two Rx antennas aft of the Tx antennastransmitting at least two different frequencies and is used to createthree-dimensional maps of the ocean floor sub-surface. In oneembodiment, the three-dimensional maps of the ocean floor sub-surfaceare to a depth under the ocean floor of at least 15 m (49.2 ft). Theradar system is towed across the survey area in a structured pattern atleast four times and as many as 20 or more. The surveys are combined tocreate three-dimensional maps of the metallic objects in the survey areaburied under the ocean floor.

FIG. 12A illustrates a three-dimensional (3D) map shown astwo-dimensional slices in the ocean floor at different depths.

FIG. 12B illustrates a 3D map indicating multiple detected objects ofvarious sizes at various depths by a radar system (e.g., a CW radarsystem) according to one embodiment of the present invention. Label “A”in FIG. 12B indicates the ocean floor. Label “B” in FIG. 12B indicates asmall slender vertically oriented target roughly 1.22 to 1.83 m (4 to 6feet) in length. Label “C” in FIG. 12B indicates a large object roughly1.83 m (6 feet) tall and 0.91 to 1.22 m (3 to 4 feet) wide at the widestpoints. The object is buried with the top approximately 6 feet down.Label “D” in FIG. 12B indicates a small object roughly 3.66 m (12 feet)below the surface of the ocean floor.

FIG. 13A illustrates a 3D underwater heat map indicating the location ofobjects according to one embodiment of the present invention. Once asurvey for a target area is performed using the radar system (e.g., theCW radar system) of the present invention, the collected data isoperable for display via mapping software. In one embodiment, thecollected data indicates information including, but not limited to, anobject and/or target signal strength, a geolocation for an object and/ortarget, a north value, a west value, an east value, and/or a southvalue. In one embodiment, the geolocation for an object and/or target isa set of coordinate points.

FIG. 13B lists all the labels in FIG. 13A representing differentgeographic locations for detected objects according to one embodiment ofthe present invention.

FIG. 14 illustrates a two-dimensional (2D) heat map indicating the radarsignal strength returned from the area providing an estimated locationcoordinates for a detected object according to one embodiment of thepresent invention. This underwater heat map indicates a sampling regionfor the radar system (e.g., the CW radar system). The 2D underwaterdepth map is shown from a South-to-North and West-to-East perspective.FIG. 14 is a fused product showing magnetometer data and ocean floortopography collected using SONAR. Area “A” labeled in FIG. 14 indicatesnumerous magnetometer detections with little or no radar returns. Thisindicates that the material is ferrous and ancient, having very poorconductivity, but strong magnetic properties. Iron canon from the early1700s is known to be in this vicinity. Area “B” in FIG. 14 illustratestwo large magnetometer detections with little or no radar returns (e.g.,similar to area “A”). Area “C” in FIG. 14 illustrates a magnetometerdetection likely of a single object of relatively small mass. Radarreturns in the vicinity indicate the object is likely a modern ironobject or steel. Area “D” in FIG. 14 illustrates the strongest radarreturn in the area with no indication of magnetometer detection,indicating non-ferrous metal in this vicinity.

FIG. 15A illustrates a 2D underwater heat map indication locationcoordinates for detected objects according to another embodiment of thepresent invention.

FIG. 15B lists all the labels in FIG. 15A representing differentgeographic locations for detected objects according to one embodiment ofthe present invention.

FIG. 16A illustrates a surveying operation with a radar system (e.g., aCW radar system) according to one embodiment of the present invention.The radar system (e.g., the CW radar system) is connected to a towingvessel. As the radar system (e.g., the CW radar system) travels overferrous and/or non-ferrous metal objects, the radar system (e.g., the CWradar system) is operable to identify a plurality of buried test sites.

FIG. 16B illustrates a surveying operation with a radar system (e.g., aCW radar system) connected to a towing vessel according to oneembodiment of the present invention. The radar system (e.g., the CWradar system) is connected to the towing vessel via a tow cable and atleast one data cable. The tow cable includes a plurality of tow cablefloats, wherein the plurality of tow cable floats are operable toprevent the tow cable and the at least one data cable from sinking belowthe surface of the water when the towing vessel is not moving.

FIG. 17A illustrates a 2D heatmap indicating the geolocation of detectedobjects according to one embodiment of the present invention. The 2Dunderwater heatmap further includes an indication of density and/orintensity. In one embodiment, the 2D underwater heatmap is overlayedwith magnetometer search tracks as illustrated in FIG. 14 . Whenoverlayed with the magnetometer, the radar system (e.g., the CW radarsystem) is able to locate all metal objects and/or targets, whilesimultaneously eliminating the ferrous objects and/or targets. In oneembodiment, the return phase and amplitude differences in each heat mapare used to distinguish between specific metal types. In one embodiment,the identification of different metal types is done automatically and innear real-time.

FIG. 17B lists all the labels in FIG. 17A representing differentpriority zones on a 2D underwater heatmap for a radar system (e.g., a CWradar system) according to one embodiment of the present invention,where priority zones represent areas where at least one or moreobject(s) and/or target(s) were detected by the radar system (e.g., theCW radar system).

FIG. 18 illustrates a 2D underwater depth map indicating the geolocationof detected objects according to another embodiment of the presentinvention.

FIG. 19A illustrates a 2D underwater heatmap indicating the geolocationof detected objects according to another embodiment of the presentinvention. The 2D underwater heatmap includes a plurality of priorityzones, indicating analyzed areas with detected objects. In addition, the2D underwater heatmap further includes a density and/or an intensity foreach priority zone.

FIG. 19B lists all the labels in FIG. 19A representing differentpriority zones on a 2D underwater heatmap for a radar system (e.g., a CWradar system) according to one embodiment of the present invention.

FIG. 20A illustrates a 2D underwater heatmap indicating a radar system(e.g., a CW radar system) traveling path and the geolocation of detectedobjects according to another embodiment of the present invention. The 2Dunderwater heatmap indicates priority zones detected by the radarsystems (e.g., the CW radar systems). The 2D underwater heatmap furtherincludes an indication of intensity and/or density for each priorityzone and/or detected object and/or target.

FIG. 20B lists all the labels in FIG. 20A representing differentgeographic locations for detected objects according to one embodiment ofthe present invention.

FIG. 21A illustrates a 2D graph indicating underwater reef and submergedsandbars (in dark brown) and a travel route for a radar system (e.g., aCW radar system) according to one embodiment of the present invention.At the beginning of a surveying operation, a target region isestablished. With the target region established, a towing vessel beginstowing the radar system (e.g., the CW radar system) in a line pattern(i.e., the travel route) over the target region. In one embodiment, thetowing vessel is connected to the radar system (e.g., the CW radarsystem) via a dinghy. A towing cable and a data cable connect the towingvessel to the dinghy, and the dinghy connects to the radar system (e.g.,the CW radar system) via a towing cable and/or data cable. In oneembodiment, the towing vessel is connected to the radar system (e.g.,the CW radar system) via a towing cable and/or data cable in addition toa dynamic winch system. The dynamic winch system is operable tofacilitate the sensor head depth during towing. In one embodiment, thetowing vessel is connected to the radar system (e.g., the CW radarsystem) via a towing cable and/or data cable in addition to the use of adynamic down plane system on or ahead of the sensor head. The dynamicdown plane system is operable to facilitate the sensor head depth duringtowing.

FIG. 21B illustrates a 2D heatmap graph indicating a travel route for aradar system (e.g., a CW radar system) according to one embodiment ofthe present invention. By repeatedly crossing over a target region, theradar system (e.g., the CW radar system) is operable to detect objectsand/or targets with greater accuracy. This is possible using thecombination of the bow and aft Rx antennas of the radar system (e.g.,the CW radar system), providing multiple opportunities for object and/ortarget detection.

FIGS. 64A-64B illustrate one embodiment of the Rx control and monitoringGUI for data collection. The raw data from the digitizers as well asprocessed real-time data are displayed to the operator. Based upon whatis shown on the GUI, the gains of the individual analog amplifier boardsare operable to be tuned (e.g., by the operator).

FIG. 64C lists all labels in FIGS. 64A-64B representing the variousmonitoring, control, and real-time analysis data and informationavailable in the GUI.

The radar system (e.g., the CW radar system) of the present inventionincludes at least one amplifier board. Current commercially-availableamplifier boards are unable to meet the amplification and dynamic rangerequirements of the present invention. Commercially available amplifierboards typically amplify at specific levels or ranges (e.g., 20-40 dB,40-60 dB, 60-80 dB, etc.). More specifically, these commercial amplifierboards only enable a user to step through each decibel range at limitedlevels (e.g., by 10 or 20 dB at each one of the available levels). Thus,these commercial amplifier boards are not sensitive enough and/or do notoffer enough dynamic and detailed control for the radar system (e.g.,the CW radar system) of the present invention. The radar system (e.g.,the CW radar system) requires a step size of approximately -19 decibels(dB) (e.g., gain steps of 0.108x, meaning if gain is 10x, the next gainstep if 10.108; if gain is 100x, next step is 100.108x; etc.), which isnot available with commercial amplifiers and amplifier boards.

In one embodiment, the at least one Rx antenna is connected to at leastone amplifier board using at least one discrete resistor networkarranged in a parallel and/or series configuration. The at least oneamplifier board is controlled by at least one switch (e.g., mechanicalswitch) and/or at least one computer-controlled relay (e.g.,autonomously via optimization software, operator action) to adjust gainof at least one amplifier on the at least one amplifier board. The atleast one amplifier is preferably ultra-low distortion and includesextremely fine selection of gain (e.g., -16.4 dB per step or smaller).

The amplifiers must be ultra-low distortion, meaning integrated circuit(IC) digital potentiometers, mechanical potentiometers, IC discreteswitching resistors, IC multiplexers and switches cannot be used as theyare either insufficiently controllable or introduce significantdistortion in the alternating current (AC) signal coming from the RxAntennas. In a preferred embodiment, the present invention makes use ofcustom designed amplifiers wherein at least one switch is used tocontrol banks of parallel and/or series resistors to control the gain ofthe amplifier stages. In one embodiment, the at least one switchincludes a mechanical dual in-line package (DIP) switch connectingindividual resistors to the amplifier control circuit. In anotherembodiment, the at least one switch includes a digitally controlled lowsignal relay switch. FIG. 74A shows the possible gain states of for anoperational amplifier using 16 resistors in series configuration. Atotal of 65,536 values are possible. FIG. 74B shows a subset of thepossible gains that are selected based upon linear gain steps. Just over4,000 unique gain values are evenly distributed between the minimumpossible gain and the maximum possible gain. FIG. 74C shows the errorbetween the actual gain settings and a theoretical perfectly lineardistribution of gain settings. FIG. 74D shows the possible gain settingsfor an Instrument Amplifier using a parallel resistor network. FIG. 74Eshows the actual gain setting used which are selected based upon lineargain steps. Just over 4,000 unique gain values are evenly distributedbetween the minimum possible and maximum possible gains. FIG. 74F showsthe error between the actual gain values that were selected and atheoretical perfectly linear distribution of gain settings.

In one embodiment, the ultra-low distortion amplifier boards have aTotal Harmonic Distortion (THD) of -123.7 dBc (0.000065%). This isaccomplished using low distortion components on the amplifier board andimplementing bandpass filters internal to the amplifier stages torestrict the propagation harmonics from initial stages of the amplifierand make the overall THD dependent mostly upon the final amplificationstage, which is selected to have very good overall performance (e.g.,ultralow noise, ultralow THD, good Gain Bandwidth Product, good slewrate, etc.).

Moreover, commercial amplifier boards experience difficulties whenbalancing two antennas within close proximity to one another, including,but not limited to, issues balancing the signal-to-noise ratio and/orissues relating to overall power output for a radar system. Traditionalamplifier boards cannot reach the decibel ranges required of the radarsystem (e.g., the CW radar system) of the present invention. The radarsystem (e.g., the CW radar system) requires the amplifier board to beable to operate between approximately 60 dB to approximately 120 dB. Theradar system (e.g., the CW radar system) also requires the amplifierboard to compensate for the DC biasing offset voltage without losingsystem gain. These functions are accomplished through hardware circuitrydesign and software control logic.

FIG. 22A illustrates an amplifier board for a radar system (e.g., a CWradar system) according to one embodiment of the present invention. Theamplifier board includes, but is not limited to, an output stage and/oran input stage. The amplifier board is operable to handle outputvoltages between approximately -10 V to approximately 10 V. In oneembodiment, the amplifier board of the present invention is athree-stage circuit. The first stage is an in-amp (instrumentationamplifier), that amplifies the differential voltage between input wires.A differential voltage is used to create the signal because the input tothe amplifier board comes from a dipole antenna that is not grounded tothe amplification board. The first stage is operable to provide up toapproximately 80 decibels (dB) of gain. In one embodiment, the firststage in-amp is operable to provide more than approximately 60 dB ofgain. The second stage is an operational amplifier (op-amp), operable toprovide up to approximately 40 dB of gain. In one embodiment, the secondstage op-amp is operable to provide approximately 60 dB of gain. Thethird stage is a band-pass filter, operable to provide approximately 2dB of gain. In one embodiment, the third stage band-pass filter isoperable to provide more than approximately 2 dB of gain.

In another embodiment, the amplifier board contains a multi-stage filterbetween the input stage (the in-amp) and the output gain stage. In oneembodiment, the filter is a sixth order low pass filter combined with atwelfth order high pass filter. Alternatively, the filter is a twelfthorder low pass filter with a sixth order high pass filter. In oneembodiment, the first filter is used on the low transmission frequencyreceivers to filter out the high frequency transmission signal, and thesecond filter is used on the high transmission frequency receivers tofilter out the low frequency transmission signal.

In another embodiment, the amplifier board has six impedance bufferedfilter stages. In a preferred embodiment, each filter stage is secondorder with a quality factor (Q) of about 1.05 to about 1.1 to increasethe rate at which the rejection band cuts in. This underlying designapproach has a multitude of different specific implementations. Twodifferent designs are operable to be used to isolate a high frequencyfrom a low frequency and/or a low frequency from a high frequency. Inthe first case, four of the filter stages are high pass and two are lowpass. In the second case, four of the filter stages are low pass and twoare high pass. Each configuration uses different cutoff frequencies toperform their isolation functions. In another embodiment, threedifferent designs are operable to be used: four low pass/two high pass,three low pass/three high pass, and two low pass/four high pass. In thisembodiment, the receivers are operable be configured for a low band, midband, and high band. Without much difficulty, it is possible toconfigure these filters such that the maximum out of band signal seen byany band is less than 2% of the intended receive frequency. This is donewith the transmit frequencies being an octave or less in separation.

In another embodiment, the amplifier boards have eight impedancebuffered second-order filters which allow a minimum of four simultaneoustransmission frequencies to be used. Performance is similar to thatdescribed in the previous paragraph.

In another embodiment, the amplifier boards have more than eightimpedance-buffered second and third-order filters which allow more thanfive simultaneous transmission frequencies.

In another embodiment, both fore and aft antennas for a band are routedto a single amplifier board. The signals are passed through individualanalog filters and then combined in an analog difference amplifier toperform time-domain signal combination and phase differencing.

FIG. 22B illustrates a pin configuration diagram for an amplifier boardfor a radar system (e.g., a CW radar system) according to one embodimentof the present invention. In one embodiment, the amplifier is an AD622amplifier board. AD622 amplifiers require only one external resistor toset any gain between approximately 2 dB and approximately 100 dB. For again of 1 dB, no external resistor is required.

FIG. 22C illustrates a pin connection diagram for an amplifier board fora radar system (e.g., a CW radar system) according to one embodiment ofthe present invention. In one embodiment, the amplifier board is anAD8429 amplifier board. AD8429 amplifier boards operate at a low cost,low power, extremely low noise, ultralow bias current, and include highspeed instrumentation suited for signal conditioning and dataacquisition applications.

FIG. 22D illustrates a pin configuration and function diagram for anamplifier board for a radar system (e.g., a CW radar system) accordingto another embodiment of the present invention.

FIG. 22E illustrates a pin configuration and function diagram for anamplifier board for a radar system (e.g., a CW radar system) accordingto another embodiment of the present invention.

FIG. 22F illustrates a chart depicting the flow of signal through anamplifier board for a radar system (e.g., a CW radar system) accordingto one embodiment of the present invention. The chart depicts fourstages of signal flow throughout the amplifier board. While stage one isalways required, the signal flow is operable to flow through anycombination of the remaining stages. By eliminating a stage from thesignal flow, the overall noise added to the radar system (e.g., the CWradar system) is reduced. In one embodiment, the flow of signal throughthe amplifier board is multi-stage and the amplification values andstages used are all computer controlled. The amplifier board furtherincludes a wiring harness operable to read all amplifier board inputsand settings, and then send the proper setting signals in order tocalibrate each board in the system. Each wiring harness includes aplurality of output control cables to Rx antennas and at least onecomputer input side. In one embodiment, the flow of the signal throughthe amplifier board depends on the location of the boat and the presenceof radiofrequency interference and noise from external sources. When theboat is closer to a populated land mass, there is increased interferencefrom power grids and other signal sources. In one embodiment, the powergrid interference includes a 60 Hz signal. In another embodiment,additional harmonics cause further interference in the system. In oneembodiment, the four-stage amplifier board is operable to eliminate theinterference via a series of filters. In another embodiment, the signaldoes not flow through all four stages of the amplifier board. In oneembodiment, the stages of amplification are chosen to reduce the amountof overall noise added to the radar system (e.g., the CW radar system).

FIG. 23 is a table for a primary gain stage of an amplifier board for aradar system (e.g., a CW radar system) according to one embodiment ofthe present invention. The primary gain stage includes resistorcombinations and settings for an Rx antenna gain controller.

FIG. 24 is a table for a secondary gain stage of an amplifier board fora radar system (e.g., a CW radar system) according to one embodiment ofthe present invention. The secondary gain stage includes resistorsettings for an Rx antenna gain controller. The various stage settingsare measured in units of ohms (Ω). In addition, the stage settingsinclude resistor settings for an Rx antenna gain controller.

FIG. 25 is a table for Stage One and Stage Two gain settings for anamplifier board for a radar system (e.g., a CW radar system) accordingto one embodiment of the present invention. The various stage settingsare measured in units of kiloohms (kΩ). In addition, the stage settingsinclude resistor settings for an Rx antenna gain controller.

The amount of gain provided by the three-stage circuit setup isindividually determined for each Rx antenna. While the antennas used,both Tx and Rx, are interchangeable, they each have their owncapacitance and performance curves. In addition, correspondinglogic-controlled circuitry enables capacitance matching between thetransmitter, amplifier, and antenna(s). This requires that each antennahave its own amplification settings, or gain, when used as a Rx antenna.In addition to this gain, the system of the present invention usesoversampling to provide an improvement in system signal-to-noise (SNR)due to processing gain. In one embodiment, the oversampling is operableto provide approximately 24 dB of SNR gain. In one embodiment, the radarsystem (e.g., the CW radar system) is operable to sample atapproximately 250,000 times a second. In addition, the amplifier boardincludes both low and high frequency pass filters, with gain controlsfrom less than approximately 2 dB to more than approximately 130 dB.

FIG. 26 is a table for gain calculations for an amplifier board for aradar system (e.g., a CW radar system) according to one embodiment ofthe present invention. The stage settings are measured in units of ohms(Ω). In addition, the stage settings include resistor settings for an Rxantenna gain controller.

FIG. 27 is a table for Stage One and Stage Two gain settings for anamplifier board for a radar system (e.g., a CW radar system) accordingto another embodiment of the present invention.

FIG. 28A is a table for resistance values for an amplifier board for aradar system (e.g., a CW radar system) according to one embodiment ofthe present invention.

FIG. 28B is a table for additional resistance values for an amplifierboard for a radar system (e.g., a CW radar system) according to oneembodiment of the present invention.

FIG. 28C is a table for additional resistance values for an amplifierboard for a radar system (e.g., a CW radar system) according to oneembodiment of the present invention.

In one embodiment, the amplifier board(s) of the radar system (e.g., theCW radar system) of the present invention operate in four stages. Thefirst stage requires the radar system (e.g., the CW radar system) toturn multiple signals into a single signal, used for object and/ortarget geolocation. Next, a low-pass anti-aliasing filter is applied tothe single signal. This low-pass filter removes unnecessary frequenciesfrom the system. The third and fourth stages are identical, and involvethe removal of noise associated with any direct current (DC) offset inorder to isolate the signal. Each stage introduces between approximately1.5 dB to approximately 271 dB gain per stage. Once the signal isisolated, the various Tx and Rx antennas are balanced, resulting in anoutput indicating the geolocation of an object and/or target. In oneembodiment, the amplifier board is digitally controlled. In oneembodiment, the amplifier board is automatically controlled. In anotherembodiment, the amplifier enables a user to select the cutoff frequencyfrom a range of approximately 106 Hz to approximately 3,000 Hz. Forlow-band frequencies, the cutoff frequency is between approximately 106Hz and approximately 280 Hz. For mid-band frequencies, the cutofffrequency is between approximately 220 Hz and approximately 650 Hz. Forhigh-band frequencies, the cutoff frequency is between approximately 500Hz and approximately 3,000 Hz.

FIG. 29 illustrates an amplifier board for a radar system (e.g., a CWradar system) according to another embodiment of the present invention.

FIG. 30 illustrates an amplifier board for a radar system (e.g., a CWradar system) according to another embodiment of the present invention.

The raw signals received by the Rx antennas are on the order of 30nanovolts. These ultra-faint signals are amplified by betweenapproximately 70 dB and approximately 120 dB of gain, with a maximumboard gain capability of more than approximately 155 dB. In oneembodiment, the typical gain of the system is between approximately100-110 dB in order to avoid saturation. In one embodiment, theamplification of the at least one amplifier board optimizes thesignal-to-noise ratio (SNR) to minimize noise from vibrations and othersources. In one embodiment, the at least one amplifier board iscontained in a two-step noise reduction system. First, impedancematching and receiver amplifier boards are housed inside shielded andgrounded metal boxes functioning as a Faraday cage, preventingelectromagnetic interference (EMI). Second, each box is housed inside athermo-electric cooler and/or heater in order to maintain a nearconstant operating temperature. This prevents thermal noise drift fromaltering the performance of the amplifier boards in any environmentalcondition.

All connectors entering the EMI boxes are shielded and grounded. Inaddition, any openings present on the EMI boxes are covered with analuminum mesh, wherein the mesh is also grounded to the EMI box. Inanother embodiment, the mesh is a copper mesh. At the frequencies usedby the radar system (e.g., the CW radar system), the aluminum meshvisually appears “open,” but in reality, is an electrical barrier to allfrequencies below approximately 10 GHz. Without EMI shielding, theamplification process is reduced by approximately 30-60 dB which isinsufficient for the signals coming from the Rx antennas. In oneembodiment, each Rx antenna in the radar system (e.g., the CW radarsystem) has its own EMI box. Each EMI box is then placed inside arefrigerated container for climate control. In one embodiment, thefrequencies used by the radar system (e.g., the CW radar system) areapproximately 3,000 Hz or less.

In one embodiment, amplification occurs in two stages. The first stageinvolves direct current (DC) removal and isolation. The DC removal andisolation techniques are described in Kresimir Odorcic (2008). “Zero DCoffset active RC filter designs,” ThinkIR: The University ofLouisville’s Institutional Repository, which is incorporated herein byreference in its entirety. Stage two represents the digitally-controlledamplification stage. By using digital relays in conjunction with fixedresistors in series-parallel networks, the radar system (e.g., the CWradar system) is able to digitally change amplification values. Thesestages include approximately 1,000,000 linear gain steps that arecapable of amplification from approximately 35 dB to approximately 156dB.

The amplifier boards used in the present invention account for allamplification processes, DC offset issues, low-pass filtering, and/orhigh-pass filtering requirements.

The radar system (e.g., the CW radar system) requires the use of adigitizer, a hardware device that receives analog information, includinglight and/or sound, and records it digitally. This process is known asdigitization. The digitizer board includes a connector box, an inputdevice for receiving input from a transmitter computing device, and/oran output device for sending output to a receiver computer device.

Digitizer boards used in the present invention are operable to takebetween approximately +10 volts (V) and approximately -10 V. Duringoperation of the radar system (e.g., the CW radar system), power levelsfluctuate due to clutter and noise issues. By operating betweenapproximately +10 V and approximately -10 V, the radar system (e.g., theCW radar system) is able to avoid saturation that occurs at voltagesgreater than approximately +10 V and less than approximately -10 V. Inaddition, operating between the range of approximately +10 V andapproximately -10 V requires approximately 3.5 decibel watt (dBW) inpower. When a detection and/or collection operation begins, the Rxantenna(s) start with a signal measuring approximately 50 nanovolts (nV)with no object and/or target detected.

All of the hardware components of the radar system (e.g., the CW radarsystem) of the present invention are subject to constant temperatureregulation as well. While no specific temperature is required, thesystem must operate at a single, constant and/or near-constanttemperature. In one embodiment, the temperature of the radar system(e.g., the CW radar system) is maintained using a thermally-controlledrefrigerator, containing the EMI-shielded amplifier boxes. The radarsystem (e.g., the CW radar system) temperature is maintained usingcooling and/or heating. The refrigerator(s) holding the EMI-shieldedamplifier boxes are operable to cool and/or heat the air around theamplifier boxes in order to reduce the amount of thermal drift in theimpedance matching and amplifier electronics. By maintaining thetemperature of the radar system (e.g., the CW radar system) at aconstant and/or near-constant temperature, the system avoidsexperiencing large temperature swings which are operable to decreasesystem accuracy, efficiency, and/or operability.

In addition to temperature issues, the radar system (e.g., the CW radarsystem) of the present invention also accounts for alternating current(AC) power issues. Because the radar system (e.g., the CW radar system)is towed, in a saltwater environment, from a vessel, the vessel presentsa grounding problem to the system. On land, grounding issues are simple:AC wiring systems including a green grounding wire, preventing shocksand electrocution. The ground connection is completed by clamping the ACwiring system to a metal water pipe or by driving a long copper stakeinto the ground. However, water-based vessels are not grounded the same.Many water-based vessels make use of a plate enabling the vessel toground itself to the ocean. Grounding for water-based vessels representsan additional source of noise that the radar system (e.g., the CW radarsystem) of the present invention must account for.

Post Processing

Post processing software is used in conjunction with the radar system(e.g., the CW radar system) of the present invention. Post processingsoftware functionality includes, but is not limited to, eliminatingvariances in boat speed, eliminating GPS timing differences across allGPS receivers used during collection, eliminating variances in computertiming across all computers used during collection, eliminatingvariances associated with the depth of the radar system (e.g., the CWradar system), real-time or near real-time object and/or targetdetection, survey automation, adjusting controls related to a towingvehicle’s navigational capabilities, object and/or targetclassification, and/or automated object and/or target identification.Object and/or target classification includes, but is not limited to,size, location, and a potential material type. In one embodiment, thepost processing software used is MATLAB (available from MATHWORKS). Inone embodiment, the post processing software used is PYTHON. In oneembodiment, the post processing software used is C/C++. In oneembodiment, the post processing software used is JAVA. In oneembodiment, the post processing software is operable to detect objectsand/or targets and their compositions in real time. In anotherembodiment, the post processing software is operable to detect objectsand/or targets and their compositions in near real time.

Post processing must also account for a direct current (DC) offset. DCoffset occurs when hardware components add DC voltage to audio signals.For example, an amplifier board of the present invention emits anadditional DC microvolt into the signals received by the Rx antenna(s).Due to the sensitivity of the system, this additional microvoltrepresents a major positive or negative shift in signal reception. Thisshift leads to a saturation in signal reception.

In addition, the radar system (e.g., the CW radar system) makes use of amulti-step process for specifically identifying objects and/or targetsof interest, as well as the material each object and/or target is madeof. In one embodiment, the multi-step process includes, but is notlimited to, raw data collection, frequency offset, frame stitching,narrow band filtering, and/or elimination of discontinuities.

Raw data collection refers to the continuous stream of data coming fromthe Rx antenna amplifier boards, as well as corresponding GPS locationdata using a towing vessel and a dinghy. In one embodiment, every ⅕^(th)second of data from the Rx antenna amplifier boards and thecorresponding GPS location data are recorded. This raw data collectionis performed using the above-mentioned digitizer boards. In oneembodiment, the digitizer boards are operable to digitize the raw dataat a rate of approximately one million bits per second. The radar system(e.g., the CW radar system) further oversamples the raw data in order toincrease the overall signal-to-noise ratio. In one embodiment,oversampling at a rate of approximately 250,000 samples per channelyields an increase in gain for the system between approximately 18 dBand approximately 26 dB.

As the radar system (e.g., the CW radar system) of the present inventiondetects both amplitudes and phase returns from objects and/or targets onor under the ocean floor, the frequency offset must be constantlymonitored and corrected for. Any transmit frequency will vary slightlywith time and environmental changes due to the electronic equipmentused. Therefore, the frequency offsets in the return signal in the Rxantennas must be continually adjusted. A constant frequency offsetfunction is applied to the raw data as it is collected by the radarsystem (e.g., the CW radar system) in order to balance out the transmitfrequency variations.

The frame stitching process involves stitching the individual data filescollected by the radar system (e.g., the CW radar system) into an array,covering hours of data collection. This frame stitching processadditionally solves for GPS and timing discontinuities. If a singlemicro-second of data is lost, this results in a discontinuity in thephase shifting, causing false signals to be inserted into the collecteddata. In order to solve this problem, in one embodiment the radar system(e.g., the CW radar system) uses at least one GPS receiver in order toreduce the loss of GPS data when closing one second of array data andstarting a new second of array data.

Once the raw data has been stitched together, a narrow band filter isapplied to the digital signal in order to eliminate the vibration andmotion of the sensor head through the water. The narrow band filter isadjustable depending upon the environmental conditions including, butnot limited to, sea-state, towing speed, depth, and/or a tow distance ofthe radar system (e.g., the CW radar system) behind a towing vesseland/or dinghy.

The last post-processing step eliminates any discontinuity associatedwith last data in the large, multi-hour array of signal data. Oncediscontinuities are eliminated, the radar system (e.g., the CW radarsystem) creates a filtered data set. Using this filtered data set, anymotion or interference effects are eliminated by taking a movingsixty-second window of data and further processing the center thirtyseconds of data in the sixty-second window. The edges of thesixty-second data file are where the aliasing effects manifest, meaningthe center thirty-seconds of data are free of these effects. Inaddition, the filtered data set is used to correct the phase offsetbetween the bow Rx antenna(s) of a specific band when compared againstthe aft Rx antenna(s) of the same specific band.

In an alternate embodiment, the entire data set is filtered using atwo-second-long filter. The digital data is taken as a single datastream from each antenna and not block processed as referenced above.This process is significantly faster than the methodology describedabove using the narrow band filter, and provides equivalent quality whenused on later model sensor heads that use smoothing design techniques toreduce vibration and jerky motion encountered with bare frame sensorhead designs.

Once the filtered data set has been phase offset corrected, the compileddata array is used to analyze the surveyed area. Any statistical data isalso stored along with the compiled array, which are both then used inconjunction with the sensor head’s GPS position with respect to thesurveyed area. In order to simplify the post-processing functions, areasbefore, during, and after a turn in a surveyed area are marked and setaside. This is because during a turn, the path of the radar system(e.g., the CW radar system) through the water varies not only indirection, but also in speed, depth, and physical orientation relativeto the surface of the water. This variance in shallow depth surveys(i.e., surveys in a body of water with a depth less than 30.5 m (100ft)) causes a rotation of the radar system (e.g., the CW radar system)when being towed from a towing vessel, such that the surface reflectionsfrom the ocean and any wave action cause excessive noise and/or falsetargeting within the collected data.

In one embodiment, the software of the radar system (e.g., the CW radarsystem) includes at least one graphical user interface (GUI). The atleast one GUI is operable to display information including, but notlimited to, Tx antenna health, Rx antenna health, object and/or targetgeolocation, a geolocation for the radar system (e.g., the CW radarsystem), a geolocation for a dinghy, a system temperature indicator, avessel status indicator, a speed indicator, an environmental temperatureindicator, an object/and or target depth indicator, an object and/ortarget material, an object and/or target size, a Tx antenna signalstatus, and/or a Rx antenna signal status.

This functionality is achieved using a combination of the radar system(e.g., the CW radar system)’s amplifier board and impedance matchingboards. Impedance matching refers to designing input impedance of anelectrical load and/or the output impedance of its corresponding signalsource in order to maximize the power transfer and/or minimize signalreflection from the electrical load. The electrical and antennacomponents of the present invention have a corresponding impedance(i.e., impedance going out from the amplifier output signal). Whentransmitting a specific signal, the radar system (e.g., the CW radarsystem) of the present invention verifies that the impedance associatedwith the electrical equipment sending the specific signal matches theimpedance of the Tx antenna sending out the signal. In addition, thereturn signal from the Rx antenna(s) must also match its impedance.

FIG. 31A illustrates the top of an impedance matching board for a radarsystem (e.g., a CW radar system) according to one embodiment of thepresent invention.

FIG. 31B illustrates the schematic of an impedance matching board for aradar system (e.g., a CW radar system) according to one embodiment ofthe present invention.

The Tx antennas require their own specialized impedance matching board.The input to this impedance matching board comes from a sound systemamplifier and the output goes directly to the Tx antennas via a datacable.

In one embodiment, the amplifier and impedance matching boards are allcomputer controlled. This enables the system to automatically and/orautonomously balance all of the values present in order to maximize thesignal going out to the Tx antennas and the signal coming back from theRx antennas.

As previously mentioned, the radar system (e.g., the CW radar system) ofthe present invention includes a multiplicity of graphical userinterfaces (GUIs), with GUIs including, but not limited to,three-dimensional (3D) maps for an underwater environment, sonartransmission and receiving, object and/or target detection mapping,receiver controls, transmission controls, and/or two-dimensional (2D)maps for an underwater environment.

FIG. 32 illustrates a graphical user interface (GUI) for displayingobjects detected by a radar system (e.g., a CW radar system) accordingto one embodiment of the present invention. The GUI is operable toprovide a three-dimensional (3D) map of a saltwater environment,indicating the presence of any detected objects and/or targets. The 3Dmap of the saltwater environment is able to be viewed from aWest-to-East and South-to-North perspective. When objects are detected,the GUI displays a double-hump-like 3D image. This occurs because anobject is first detected by the bow Rx antennas of the radar system(e.g., the CW radar system), creating a rise in signal strength. Thisdetected signal strength drops as the bow of the radar system (e.g., theCW radar system) passes over the detected object. Then, as the aft Rxantennas of the radar system (e.g., the CW radar system) detect theobject, a second rise in signal strength is detected. As the aft of theradar system (e.g., the CW radar system) moves away from the detectedobject, a drop in signal strength occurs. The combination of the bow andaft Rx antenna detections results in a double-hump-shape on the GUI,indicating that an object has been detected. In one embodiment, theradar system (e.g., the CW radar system) is operable to detect andidentify objects and/or targets in real time or near-real time. Themovement of the radar system (e.g., the CW radar system) generates 2Dand 3D images of the target survey area with a multiplicity of lines.

FIG. 33 illustrates a GUI for displaying objects detected by a radarsystem (e.g., a CW radar system) according to another embodiment of thepresent invention. The GUI displaying the 3D map of the saltwaterenvironment is able to be viewed from a South-to-North and West-to-Eastperspective.

FIG. 34 illustrates a sonar GUI for a radar system (e.g., a CW radarsystem) according to one embodiment of the present invention. The sonarGUI is operable to display elements including, but not limited to, astart recording time, an end recording time, a heading, a range, adistance, a measurement of the distance divided by a sonar ping, analtitude, a travel route, an inline stretch value, a range limit, a viewselection drop-down box, a channel selection, a color scheme selection,an auto refresh option, a compass, a list of detected objects and/ortargets, and/or a tile identification (ID) number.

FIG. 35 illustrates a travel route GUI for a radar system (e.g., a CWradar system) that shows the position of the tow vessel, the shallow towassist vessel (dingy), and the real-time calculated position of theradar sensor (all three indicated by the box) according to oneembodiment of the present invention. The travel route GUI is operable todisplay information including, but not limited to, a travel route forthe radar system (e.g., the CW radar system), an object and/or targetdetection indication, and/or a depth value. The travel route for theradar system (e.g., the CW radar system) is displayed as a green line,indicating the positions the radar system (e.g., the CW radar system)has traveled over. As the radar system (e.g., the CW radar system)continuously travels over a target region, objects and/or targets aredetected by the Rx antennas at the bow and aft of the radar system(e.g., the CW radar system). The stronger the received signal by the Rxantennas, the darker the indication on the map (e.g., the red dots onthe map). A cluster of red dots is also an indication of a detectedobject and/or target, as this indicates a strong signal detected by thebow and aft Rx antennas. In one embodiment, the travel route GUI isdisplayed using color images. In one embodiment, the travel route GUI isdisplayed in black and white images.

FIG. 36A illustrates a two-dimensional (2D) map indicating a log scaleof a normalized energy product for a radar system (e.g., a CW radarsystem) with no detected targets according to one embodiment of thepresent invention. The lack of detected objects is indicated by theabsence of connecting lines between target points. As the radar system(e.g., the CW radar system) travels over a region, objects are firstdetected by the bow Rx antennas and then detected a second time by theaft Rx antennas. This detection pattern is visualized by solid lines,indicating that an object and/or target was detected by both sets of Rxantennas as the radar system (e.g., the CW radar system) passed over theobject and/or target.

FIG. 36B illustrates a 2D map indicating a log scale of a normalizedenergy product for a radar system (e.g., a CW radar system) withdetected targets according to another embodiment of the presentinvention. Detected objects are indicated by the presence of connectingred lines between target zones. These red lines indicate that both thebow and aft Rx antennas received a corresponding return signal from anobject and/or target. This occurs as the bow Rx antennas cross over adetected object and/or target and then move away from the detectedobject and/or target, with the aft Rx antennas then detecting the objectand/or target followed by an increase in distance from the object and/ortarget. Thus, an object is detected by the radar system (e.g., the CWradar system) twice, once as the bow Rx antennas are towed over theobject and a second time as the aft Rx antennas are towed over theobject. This results in increased accuracy relating to object and/ortarget detection of both ferrous and non-ferrous metals in saltwaterenvironments.

FIG. 37A illustrates a 2D density and intensity map for a radar system(e.g., a CW radar system) according to one embodiment of the presentinvention.

FIG. 37B illustrates a 2D density map for a radar system (e.g., a CWradar system) according to one embodiment of the present invention.

FIG. 38 illustrates a GUI for displaying energy and frequency dataassociated with a radar system (e.g., a CW radar system) according toone embodiment of the present invention. The GUI is operable to displayinformation including, but not limited to, a graph indicating an energyof difference of time domain signals, a graph indicating a product ofenergy, a graph indicating a standard deviation from antennas and powerdensity, a graph indicating a difference in power history, a surveytrack map, a boat speed and/or direction, a time, a channel 1 frequency,a channel 1 power value, a channel 2 frequency, a channel 2 power value,a mean, a standard deviation, a frequency offset value, a set of averagephase values, a peak frequency distance, and/or a normalized energyproduct value. The red and blue lines correspond to the signal returnfrom two Rx antennas. The green line is the power density spectrumcalculation, which is derived from the signal return of the Rx antennas.The GUI is further operable to display a survey track in the lower rightcorner of the GUI. In another embodiment, the GUI has a set(s) ofuser-defined windows to monitor, track, and display variouscomponent(s), system(s), and external values.

FIG. 39 illustrates a GUI for displaying phase detail and power historydata associated with a radar system (e.g., a CW radar system) accordingto one embodiment of the present invention. The GUI is operable todisplay information including, but not limited to, a graph indicatingsubsecond phase detail, a graph indicating subsecond power history forboth a bow and aft normalized energy product, and/or a graph indicatinga subsecond difference power history using a mean and standarddeviation. The blue and red lines correspond to a signal return from twoRx antennas. The green line is a power density spectrum calculationderived from the signal return from the two Rx antennas.

In another embodiment of the processing scheme, the fore and aft Rxantennas for at least two frequencies from at least two sets of Rxantennas are subject to phase array processing by time shifting thesamples from the array based on time-distance calculations usinginformation from the multi-GPS geolocation system. This has the impactof focusing the receive beams directly to the side of the sensor headand even with the Tx antennas.

In another embodiment of the processing scheme, the at least twofrequencies which are now centered on the respective Tx antennas areagain time shifted such that both frequencies are synchronized in timeand space. The processing then compares the at least two frequencies forhow the constructive and destructive zones are aligned and theapproximate range to the target object is calculated. Next, all data forthe survey area is similarly processed and mapped. The peak signalswhere multiple survey lines overlap are determined and the softwareidentifies those possible target locations. FIG. 65 is an illustrationof the resulting Automatic Target Cueing product which identifies themost likely target location. The targets “cued” by the software areindicated by the white text filed boxes which show their location andsignal strength.

In another embodiment, returns from multiple depths are hypothesized foreach target and software then tests each hypothesis. The results frommultiple runs are then overlayed and processed using a correlationfilter. The result is a three-dimensional map of the sub-ocean floormetal distribution. FIG. 12A illustrates one such site where slices ofthe sub-ocean floor are taken at 0.91 m (3 ft) intervals once the firstobject is detected.

FIG. 40 is a schematic diagram of an embodiment of the inventionillustrating a computer system, generally described as 800, having anetwork 810, a plurality of computing devices 820, 830, 840, a server850, and a database 870.

The server 850 is constructed, configured, and coupled to enablecommunication over a network 810 with a plurality of computing devices820, 830, 840. The server 850 includes a processing unit 851 with anoperating system 852. The operating system 852 enables the server 850 tocommunicate through network 810 with the remote, distributed userdevices. Database 870 is operable to house an operating system 872,memory 874, and programs 876.

In one embodiment of the invention, the system 800 includes a network810 for distributed communication via a wireless communication antenna812 and processing by at least one mobile communication computing device830. Alternatively, wireless and wired communication and connectivitybetween devices and components described herein include wireless networkcommunication such as WI-FI, WORLDWIDE INTEROPERABILITY FOR MICROWAVEACCESS (WIMAX), Radio Frequency (RF) communication including RFidentification (RFID), NEAR FIELD COMMUNICATION (NFC), BLUETOOTHincluding BLUETOOTH LOW ENERGY (BLE), ZIGBEE, Infrared (IR)communication, cellular communication, satellite communication,Universal Serial Bus (USB), Ethernet communications, communication viafiber-optic cables, coaxial cables, twisted pair cables, and/or anyother type of wireless or wired communication. In another embodiment ofthe invention, the system 800 is a virtualized computing system capableof executing any or all aspects of software and/or applicationcomponents presented herein on the computing devices 820, 830, 840. Incertain aspects, the computer system 800 is operable to be implementedusing hardware or a combination of software and hardware, either in adedicated computing device, or integrated into another entity, ordistributed across multiple entities or computing devices.

By way of example, and not limitation, the computing devices 820, 830,840 are intended to represent various forms of electronic devicesincluding at least a processor and a memory, such as a server, bladeserver, mainframe, mobile phone, personal digital assistant (PDA),smartphone, desktop computer, netbook computer, tablet computer,workstation, laptop, and other similar computing devices. The componentsshown here, their connections and relationships, and their functions,are meant to be exemplary only, and are not meant to limitimplementations of the invention described and/or claimed in the presentapplication.

In one embodiment, the computing device 820 includes components such asa processor 860, a system memory 862 having a random access memory (RAM)864 and a read-only memory (ROM) 866, and a system bus 868 that couplesthe memory 862 to the processor 860. In another embodiment, thecomputing device 830 is operable to additionally include components suchas a storage device 890 for storing the operating system 892 and one ormore application programs 894, a network interface unit 896, and/or aninput/output controller 898. Each of the components is operable to becoupled to each other through at least one bus 868. The input/outputcontroller 898 is operable to receive and process input from, or provideoutput to, a number of other devices 899, including, but not limited to,alphanumeric input devices, mice, electronic styluses, display units,touch screens, signal generation devices (e.g., speakers), or printers.

By way of example, and not limitation, the processor 860 is operable tobe a general-purpose microprocessor (e.g., a central processing unit(CPU)), a graphics processing unit (GPU), a microcontroller, a DigitalSignal Processor (DSP), an Application Specific Integrated Circuit(ASIC), a Field Programmable Gate Array (FPGA), a Programmable LogicDevice (PLD), a controller, a state machine, gated or transistor logic,discrete hardware components, or any other suitable entity orcombinations thereof that can perform calculations, process instructionsfor execution, and/or other manipulations of information.

In another implementation, shown as 840 in FIG. 40 , multiple processors860 and/or multiple buses 868 are operable to be used, as appropriate,along with multiple memories 862 of multiple types (e.g., a combinationof a DSP and a microprocessor, a plurality of microprocessors, one ormore microprocessors in conjunction with a DSP core).

Also, multiple computing devices are operable to be connected, with eachdevice providing portions of the necessary operations (e.g., a serverbank, a group of blade servers, or a multi-processor system).Alternatively, some steps or methods are operable to be performed bycircuitry that is specific to a given function.

According to various embodiments, the computer system 800 is operable tooperate in a networked environment using logical connections to localand/or remote computing devices 820, 830, 840 through a network 810. Acomputing device 830 is operable to connect to a network 810 through anetwork interface unit 896 connected to a bus 868. Computing devices areoperable to communicate communication media through wired networks,direct-wired connections or wirelessly, such as acoustic, RF, orinfrared, through an antenna 897 in communication with the networkantenna 812 and the network interface unit 896, which are operable toinclude digital signal processing circuitry when necessary. The networkinterface unit 896 is operable to provide for communications undervarious modes or protocols.

In one or more exemplary aspects, the instructions are operable to beimplemented in hardware, software, firmware, or any combinationsthereof. A computer readable medium is operable to provide volatile ornon-volatile storage for one or more sets of instructions, such asoperating systems, data structures, program modules, applications, orother data embodying any one or more of the methodologies or functionsdescribed herein. The computer readable medium is operable to includethe memory 862, the processor 860, and/or the storage media 890 and isoperable be a single medium or multiple media (e.g., a centralized ordistributed computer system) that store the one or more sets ofinstructions 900. Non-transitory computer readable media includes allcomputer readable media, with the sole exception being a transitory,propagating signal per se. The instructions 900 are further operable tobe transmitted or received over the network 810 via the networkinterface unit 896 as communication media, which is operable to includea modulated data signal such as a carrier wave or other transportmechanism and includes any delivery media. The term “modulated datasignal” means a signal that has one or more of its characteristicschanged or set in a manner as to encode information in the signal.

Storage devices 890 and memory 862 include, but are not limited to,volatile and non-volatile media such as cache, RAM, ROM, EPROM, EEPROM,FLASH memory, or other solid state memory technology; discs (e.g.,digital versatile discs (DVD), HD-DVD, BLU-RAY, compact disc (CD), orCD-ROM) or other optical storage; magnetic cassettes, magnetic tape,magnetic disk storage, floppy disks, or other magnetic storage devices;or any other medium that can be used to store the computer readableinstructions and which can be accessed by the computer system 800.

In one embodiment, the computer system 800 is within a cloud-basednetwork. In one embodiment, the server 850 is a designated physicalserver for distributed computing devices 820, 830, and 840. In oneembodiment, the server 850 is a cloud-based server platform. In oneembodiment, the cloud-based server platform hosts serverless functionsfor distributed computing devices 820, 830, and 840.

In another embodiment, the computer system 800 is within an edgecomputing network. The server 850 is an edge server, and the database870 is an edge database. The edge server 850 and the edge database 870are part of an edge computing platform. In one embodiment, the edgeserver 850 and the edge database 870 are designated to distributedcomputing devices 820, 830, and 840. In one embodiment, the edge server850 and the edge database 870 are not designated for distributedcomputing devices 820, 830, and 840. The distributed computing devices820, 830, and 840 connect to an edge server in the edge computingnetwork based on proximity, availability, latency, bandwidth, and/orother factors.

It is also contemplated that the computer system 800 is operable to notinclude all of the components shown in FIG. 40 , is operable to includeother components that are not explicitly shown in FIG. 40 , or isoperable to utilize an architecture completely different than that shownin FIG. 40 . The various illustrative logical blocks, modules, elements,circuits, and algorithms described in connection with the embodimentsdisclosed herein are operable to be implemented as electronic hardware,computer software, or combinations of both. To clearly illustrate thisinterchangeability of hardware and software, various illustrativecomponents, blocks, modules, circuits, and steps have been describedabove generally in terms of their functionality. Whether suchfunctionality is implemented as hardware or software depends upon theparticular application and design constraints imposed on the overallsystem. Skilled artisans may implement the described functionality invarying ways for each particular application (e.g., arranged in adifferent order or partitioned in a different way), but suchimplementation decisions should not be interpreted as causing adeparture from the scope of the present invention.

FIG. 41 illustrates an amplifier board for a radar system (e.g., a CWradar system) according to one embodiment of the present invention.

FIG. 42 illustrates an amplifier board for a radar system (e.g., a CWradar system) according to another embodiment of the present invention.

FIG. 43 illustrates an amplifier board for a radar system (e.g., a CWradar system) according to yet another embodiment of the presentinvention.

FIG. 44 illustrates an amplifier board for a radar system (e.g., a CWradar system) according to yet another embodiment of the presentinvention.

FIG. 45 illustrates an amplifier board for a radar system (e.g., a CWradar system) according to yet another embodiment of the presentinvention.

FIG. 46 illustrates an amplifier board for a radar system (e.g., a CWradar system) according to yet another embodiment of the presentinvention.

The above-mentioned examples are provided to serve the purpose ofclarifying the aspects of the invention, and it will be apparent to oneskilled in the art that they do not serve to limit the scope of theinvention. By nature, this invention is highly adjustable, customizableand adaptable. The above-mentioned examples are just some of the manyconfigurations that the mentioned components can take on. Allmodifications and improvements have been deleted herein for the sake ofconciseness and readability but are properly within the scope of thepresent invention.

1. A radar system for detecting ferrous and non-ferrous metals in anunderwater environment, comprising: at least one support vessel; and anantenna system including at least one signal generator, at least onetransmitter (Tx) antenna, at least one receiver (Rx) antenna, and atleast one signal processor; wherein the at least one Tx antenna and theat least one Rx antenna are fixed in a cross-polarized orientation witheach other or electrically isolated by distance and/or topography;wherein the at least one Rx antenna is substantially perpendicular to adirection of travel of the at least one support vessel; wherein the atleast one signal generator is operable to emit at least one transmissionsignal to a target area through the at least one Tx antenna; wherein theat least one transmission signal is an extremely low frequency (ELF)signal; wherein the at least one Rx antenna is operable to receive atleast one return signal from the target area; wherein the at least onesignal processor is operable to analyze the at least one return signal;wherein the at least one signal processor is operable to detect and/orlocate at least one target object in the target area based on the atleast one return signal; and wherein the underwater environment is asaltwater environment.
 2. The system of claim 1, further comprising agraphical user interface (GUI), wherein the GUI is operable to display avisualization of the at least one target object in the target area. 3.The system of claim 1, wherein the antenna system includes a pluralityof Rx antennas for each of the at least one Tx antennas.
 4. The systemof claim 1, wherein the at least one transmission signal is a pluralityof transmission signals, and wherein the plurality of transmissionsignals includes at least two different frequencies and/or at least twodifferent power levels.
 5. The system of claim 1, wherein the at leastone signal processor is operable to identify at least one constructiveinterference zone and at least one destructive interference zone in thetarget area.
 6. The system of claim 1, wherein the support vessel is anactive tow fish, a remotely operated vehicle (ROV), or an autonomousunderwater vehicle (AUV).
 7. The system of claim 1, wherein informationfrom the at least one signal processor is transmitted to land-basedand/or water-based systems via fiber-optic communication, wiredcommunication, and/or low frequency sub-channel radio frequency (RF)communication.
 8. The system of claim 1, wherein the at least one signalprocessor is operable to distinguish between different types of metalcomprising the at least one target object.
 9. The system of claim 1,wherein the at least one Tx antenna and the at least one Rx antennaincludes a plurality of Tx antennas and a plurality of Rx antennas,wherein the plurality of Tx antennas and the plurality of Rx antennasare interlinked via fiber-optic communication, wired communication,and/or low frequency sub-channel radio frequency (RF) communication. 10.The system of claim 1, wherein the at least one Tx antenna and the atleast one Rx antenna includes a plurality of Tx antennas and a pluralityof Rx antennas, wherein the plurality of Tx antennas and the pluralityof Rx antennas are arranged in a pattern to form a radio frequency (RF)fence, and wherein the radar system is operable to identify movementacross the RF fence.
 11. The system of claim 1, wherein the at least oneRx antenna includes a plurality of Rx antennas, wherein the plurality ofRx antennas is arranged in at least two parallel lines.
 12. The systemof claim 1, wherein the radar system is operable to identify a locationand/or a travel direction for surface vessels, sub-surface vessels,and/or divers in the target area.
 13. In one embodiment, the systemfurther includes at least one amplifier board, wherein the at least oneRx antenna is connected to the at least one amplifier board using atleast one discrete resistor network arranged in a parallel and/or seriesconfiguration, and wherein at least one switch and/or at least onedigitally controlled relay is operable to adjust gain on at least oneamplifier on the at least one amplifier board.
 14. In one embodiment,the system further includes at least one amplifier board, wherein the atleast one amplifier board includes at least one narrow band filter toallow at least one high power out-of-band signal to be transmittedwithout interfering with reception of at least one in-band signal.
 15. Aradar system for detecting ferrous and non-ferrous metals in anunderwater environment, comprising: at least one support vessel; anantenna system including at least one signal generator, at least onetransmitter (Tx) antenna, at least one receiver (Rx) antenna, and atleast one signal processor; and a geolocation system; wherein the atleast one Tx antenna and the at least one Rx antenna are fixed in across-polarized orientation with each other or electrically isolated bydistance and/or topography; wherein the at least one Rx antenna issubstantially perpendicular to a direction of travel of the at least onesupport vessel; wherein the at least one signal generator is operable toemit at least one transmission signal to a target area through the atleast one Tx antenna; wherein the at least one transmission signal is anextremely low frequency (ELF) signal; wherein the at least one Rxantenna is operable to receive at least one return signal from thetarget area; wherein the at least one signal processor is operable toanalyze the at least one return signal; wherein the at least one signalprocessor is operable to detect and/or locate at least one target objectin the target area based on the at least one return signal; wherein theat least one signal processor is operable to determine a relativegeolocation and/or an absolute geolocation of the at least one targetobject using the geolocation system; and wherein the underwaterenvironment is a saltwater environment.
 16. The system of claim 15,wherein the geolocation system includes a plurality of signal reflectorsin the underwater environment.
 17. The system of claim 15, wherein thegeolocation system includes at least one global positioning system (GPS)module.
 18. A method for detecting ferrous and non-ferrous metals in anunderwater environment, comprising: at least one support vesseltraversing a target area; at least one signal generator emitting atleast one transmission signal to the target area through at least onetransmitter (Tx) antenna; at least one receiver (Rx) antenna receivingat least one return signal from the target area; at least one signalprocessor analyzing the at least one return signal; and the at least onesignal processor detecting and/or locating at least one target object inthe target area based on the at least one return signal; wherein the atleast one transmission signal is an extremely low frequency (ELF)signal; wherein the at least one Tx antenna and the at least one Rxantenna are fixed in a cross-polarized orientation with each other;wherein the at least one Rx antenna is substantially perpendicular to adirection of travel of the at least one support vessel; and wherein theunderwater environment is a saltwater environment.
 19. The method ofclaim 18, further comprising the support vessel traversing at least oneportion of the target area multiple times.
 20. The method of claim 18,wherein the at least one transmission signal is a plurality oftransmission signals, wherein the plurality of transmission signalsincludes at least two frequencies and/or at least two power levels. 21.The method of claim 18, further comprising the at least one signalprocessor identifying at least one constructive interference zone and atleast one destructive interference zone in the target area.
 22. Themethod of claim 18, further comprising adjusting gain of at least oneamplifier on at least one amplifier board using at least one switchand/or at least one digitally controlled relay, wherein the at least oneRx antenna is connected to the at least one amplifier board using atleast one discrete resistor network arranged in a parallel and/or seriesconfiguration.
 23. The method of claim 18, further comprising the atleast one signal processor identifying at least one metal comprising theat least one target object.
 24. The method of claim 18, furthercomprising the at least one signal processor determining athree-dimensional (3D) distribution of the at least one target object onand/or below a floor of the underwater environment.